Dual variable color measuring system

ABSTRACT

A measuring system performs measurement of two measured values and simultaneously exhibits the two measurement results in a digital format on a single variable color display device in respectively different colors, in order to distinguish them comfortably.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of my application Ser. No. 08/910,080, filed on Aug.12, 1997, entitled Variable Color Display System, now U.S. Pat. No.6,018,237 which is a division of my application Ser. No. 08/571,246,filed on Dec. 12, 1995, entitled Variable Color Display System, now U.S.Pat. No. 5,656,935 issued on Aug. 12, 1997, which is a division of myapplication Ser. No. 08/187,350, filed on Jan. 27, 1994, entitledVariable Color Digital Multimeter, now U.S. Pat. No. 5,475,300 issued onDec. 12, 1995, which is a division of my application Ser. No.07/865,460, filed on Apr. 9, 1992, entitled Variable Color DigitalMultimeter, now U.S. Pat. No. 5,283,517 issued on Feb. 1, 1994, which isa division of my application Ser. No. 07/628,328, filed on Dec. 14,1990, entitled Variable Color Digital Multimeter, now U.S. Pat. No.5,122,733 issued on Jun. 16, 1992, which is a division of my applicationSer. No. 07/197,322, filed on May 23, 1988, entitled Variable ColorDigital Multimeter, now abandoned, which is a division of my applicationSer. No. 06/819,111, filed on Jan. 15, 1986, entitled Variable ColorDigital Multimeter, now U.S. Pat. No. 4,794,383 issued on Dec. 27, 1988.

Reference is also made to my related applications Ser. No. 06/817,114,filed on Jan. 8, 1986, entitled Variable Color Digital Timepiece, nowU.S. Pat. No. 4,647,217 issued on Mar. 3, 1987, Ser. No. 06/919,425,filed on Oct. 16, 1986, entitled Electronic Timepiece with transducers,now U.S. Pat. No. 4,687,340 issued on Aug. 18, 1987, Ser. No.06/926,511, filed on Nov. 3, 1986, entitled Electronic Timepiece withPhysical Transducer, now U.S. Pat. No. 4,705,406 issued on Nov. 10,1987, Ser. No. 07/150,913, filed on Feb. 1, 1988, entitled VariableColor Display Typewriter, now U.S. Pat. No. 4,824,269 issued on Apr. 25,1989, Ser. No. 07/336,080, filed on Apr. 11, 1989, entitled VariableColor Display Typewriter, now U.S. Pat. No. 4,934,852 issued on Jun. 19,1990, Ser. No. 06/839,526, filed on Mar. 14, 1986, entitled VariableColor Display Telephone, now U.S. Pat. No. 4,726,059 issued on Feb. 16,1988, Ser. No. 06/940/100, filed on Dec. 10, 1986, entitled DigitalVoltmeter with Variable Color Background, now U.S. Pat. No. 4,831,326issued on May 16, 1989, Ser. No. 06/922,847, filed on Oct. 24, 1986,entitled Continuously Variable Color Display Device, now U.S. Pat. No.4,845,481 issued on Jul. 4, 1989, Ser. No. 07/322,341, filed on Mar. 13,1989, entitled Continuously Variable Color Optical Device, now U.S. Pat.No. 4,965,561 issued on Oct. 23, 1990, Ser. No. 07/379,616, filed onJul. 14, 1989, entitled Variable Color Digital Display for EmphasizingPosition of Decimal Point, now U.S. Pat. No. 5,003,298 issued on Mar.26, 1991, Ser. No. 06/920,740, filed on Oct. 20, 1986, entitled StepVariable Color Display Device, now abandoned, Ser. No. 06/931,626, filedon Nov. 17, 1986, entitled Variable Color Hybrid Display Device, nowabandoned, Ser. No. 07/157,603, filed on Feb. 19, 1988, entitledVariable Color Multiplexed Display System, now abandoned, and Ser. No.07/000,478, filed on Jan. 5, 1987, entitled Variable Color DigitalTachometer, now abandoned, which describe the devices employing avariable color display.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to measuring instruments utilizing a variablecolor digital display.

2. Description of the Prior Art

A display device described in U.S. Pat. No. 3,740,570, issued on Jun.19, 1973 to George R. Kaelin et al., uses special LEDs that exhibitdifferent colors when subjected to different currents. The LEDs arebiased by pulses of different amplitudes, to achieve different colors ofthe display, and by the length inversely proportional to the pulseamplitude, to compensate for variable brightness of the display causedby different amplitudes of the pulses.

A circuit employing a dual-color LED driven by a dual timer is describedin the article by Bill Wagner entitled 2-color LED+driver=versatilevisual effects, published on Oct. 2, 1980 in EDN volume 25, No. 19, page164. Since dual-color LEDs are connected to conduct currents in oppositedirections, it would be impossible to forwardly bias themsimultaneously.

An electronic display having segments wherein each segment is capable ofselectively illuminating two colors is disclosed in U.S. Pat. No.4,488,149 issued on Dec. 11, 1984 to William A. Givens, Jr. Two ANDgates are provided for biasing, in each display segment, either a firstlight emitting diode, for emitting a first color, or a second lightemitting diode, for emitting a second color. It is not contemplated toilluminate both light emitting diodes in each segment simultaneously forblending the colors.

A multi-colour LED display for seven segment figures is disclosed inGerman Patent No. 3,009,416 issued on Sep. 17, 1981 to Klaus Gillessen.The LED circuit consists of seven group of diodes, each group made up oftwo diodes, one red and one green. The cathodes of all red diodes areterminated in a common connection, and the green ones likewise, theanodes of each pair of diodes being common for that pair. Twotransistors connected in cascade are utilized for activating either allgreen LEDs, or all red LEDs, but not both simultaneously. When a lowlevel signal is applied to the base of the first transistor, the firsttransistor is blocked, and the second transistor is turned ON toilluminate the second set of the diodes. When a high level signal isapplied to the input of the first transistor, the first transistor isturned ON, while the second transistor is blocked, whereby the first setof the diodes is illuminated. Since the first transistor cannot besimultaneously turned ON and OFF, it would be impossible to illuminatethe two sets of the diodes simultaneously. In another embodiment isshown a multi-colour LED display utilizing three sets of LEDs: red,green, and blue, which are respectively commonly connected and may beactivated by manual switches. It is not contemplated that the three setsof LEDs be activated in selective combinations to blend the colors.

A digital electrooptical display with anti-parallel light emittingdiodes is disclosed in East German Patent No. 220,844 issued on Apr. 10,1985 to Thomas Hoffmann et al. Two light emitting diodes for emittinglight of different colors are connected in each segment back-to-back.Since the light emitting diodes are connected to conduct currents inopposite directions, it would be impossible to illuminate themsimultaneously, because the opposite currents attempting to pass througha single conductor would cancel.

A system for measuring radioactivity is described in U.S. Pat. No.2,643,344, issued on Jun. 23, 1953 to Ian H. McLaren et al. Anothersystems for measuring radioactivity are described in U.S. Pat. No.2,648,015 issued on Aug. 4, 1953 to Alexander Greenfield et al., and inU.S. Pat. No. 2,682,000 issued on Jun. 22, 1954 to Joseph F. Clayton etal. Since these three patents are very similar, they are equallyauthoritative. The system for measuring radioactivity, disclosed in thethree patents, includes an analog pointer indicator having three scales,with three associated colored light bulbs, for indicating which scale isapplicable for the reading of the measured value. A mechanism forautomatic range selection is provided, which is controlled by twosolenoids, and which also controls the three associated colored lightbulbs. In response to the range selection, one of the light bulbsilluminates the indicator face with a distinctive color to indicatewhich measurement scale is applicable.

A digital meter is disclosed in U.S. Pat. No. 2,889,518, issued on Jun.2, 1959 to Harold R. Hudson et al. The digital meter includes a motor, awheel counter rotatable by the motor, a potentiometer rotatable by themotor, and a mechanical sampler (vibrator). An unknown voltage iscompared, by the sampler, with an instant reference voltage that appearson the wiper of the potentiometer. The motor keeps rotating thepotentiometer until the unknown voltage is equal to the referencevoltage. The rotation of the motor is then automatically stopped, whichalso stops the wheel counter, whose position numerically indicates thevalue of the measured voltage. The decimal point monochromatic lamps areplaced between the wheels of the counter. One of the decimal point lampsis illuminated, by manually operated range switch, to indicate by itsposition the selected measurement range.

The prior art measuring instruments do not contemplate that the digitalindications of two different measured values may be simultaneouslyexhibited on a single display device and distinguished by differentcolors.

SUMMARY OF THE INVENTION

In a broad sense, it is the principal object of this invention toprovide an improved variable color digital measuring instrument.

It is still another object of the invention to provide a dual measuringsystem having a single light emitting diode display device forexhibiting both measurement results.

It is still another object of the invention to provide a variable colordigital measuring system for distinguishing two digital indications oftwo different measured values by different colors.

It is still another object of the invention to provide a measuringsystem with a variable color digital display device controlled by twosimultaneously applied color control signals.

In summary, a measuring system is disclosed for measuring twoindependent input signals and for providing two digital indications ofthe measured values of the two signals on a single variable color lightemitting diode display device which includes a plurality of side by sidepositioned display elements.

The invention resides in the provision of a color control forsimultaneously developing two color control signals, for illuminatingthe first digital indication in a first color, and for illuminating thesecond digital indication in a second color, in order to distinguishthem comfortably. The two color control signals may be developed eitherby a technique of a continuously variable color control or by atechnique of a step variable color control, as will be described indetail subsequently.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings in which are shown several possible embodiments of theinvention,

FIG. 1 is a block diagram of a typical prior art monochromatic digitaldisplay system.

FIG. 2 is a generalized block diagram of a variable color digitaldisplay system for the practice of the present invention.

FIG. 3 is a block diagram of a step variable color display system.

FIG. 4 is a block diagram of a continuously variable color displaysystem.

FIG. 5 is a block diagram of 2-primary color digital display.

FIG. 6 is a block diagram of 3-primary color digital display.

FIG. 7 is an enlarged detail of one digit of 2-primary color digitaldisplay.

FIG. 8 is an enlarged cross-sectional view of one display segment inFIG. 7, taken along the line 8—8.

FIG. 9 is an enlarged detail of one digit of 3-primary color digitaldisplay.

FIG. 10 is an enlarged cross-sectional view of one display segment inFIG. 9, taken along the line 10—10.

FIG. 11 is a schematic diagram of one digit of 2-primary color controlcircuit of this invention.

FIG. 12 is a schematic diagram of one digit of 3-primary color controlcircuit of this invention.

FIG. 13 is a block diagram of a color control logic circuit forcontrolling 2-primary color display.

FIG. 14 is a block diagram of a color control logic circuit forcontrolling 3-primary color display.

FIG. 15 is a schematic diagram of a color control logic circuit forcontrolling 2-primary color display.

FIG. 16 is a schematic diagram of a color control logic circuit forcontrolling 3-primary color display.

FIG. 17 is a simplified schematic diagram, similar to FIG. 11, showinghow the number ‘7’ can be displayed in three different colors.

FIG. 18 is a simplified schematic diagram, similar to FIG. 12, showinghow the number ‘1’ can be displayed in seven different colors.

FIG. 19 is a block diagram of 2-primary color 4-digit display.

FIG. 20 is a block diagram of 3-primary color 4-digit display.

FIG. 21 is a block diagram of a signal converter for 2-primary colordisplay.

FIG. 22 is a block diagram of a signal converter for 3-primary colordisplay.

FIG. 23 is a schematic diagram of a comparator circuit for 2-primarycolor display.

FIG. 24 is a graph showing the relationship between the inputs andoutputs of the comparator circuit in FIG. 23.

FIG. 25 is a schematic diagram of a comparator circuit for 3-primarycolor display.

FIG. 26 is a graph showing the relationship between the inputs andoutputs of the comparator circuit in FIG. 25.

FIG. 27 is a block diagram of a continuously variable color displaysystem utilizing two primary colors.

FIG. 28 is a block diagram of a continuously variable color displaysystem utilizing three primary colors.

FIG. 29 is an expanded block diagram of FIG. 27.

FIG. 30 is an expanded block diagram of FIG. 28.

FIG. 31 is a schematic diagram of a scaling circuit.

FIG. 32 is a schematic diagram of an A/D converter and memorycombination of FIGS. 29 and 30.

FIG. 33 is a schematic diagram of a memory and color convertercombination of FIG. 29.

FIG. 34 is a timing diagram of the circuit shown in FIG. 33.

FIG. 35 is a schematic diagram of a memory and color convertercombination of FIG. 30.

FIG. 36 is a timing diagram of the circuit shown in FIG. 35.

FIG. 37 is a continuation of the timing diagram of FIG. 36.

FIG. 38 is a graphic representation of TABLE 1.

FIG. 39 is a graphic representation of TABLE 2.

FIG. 40 is a graph of the ICI chromaticity diagram.

FIG. 41 is a block diagram of a multimeter with variable color digitaldisplay.

FIG. 42 is a block diagram of a multimeter with multiplexed variablecolor digital display.

FIG. 43 is a block diagram of a digital multimeter with a display thatcan change color in accordance with external control.

FIG. 44 is a block diagram of a digital multimeter with a display thatcan change color in accordance with internal control.

FIG. 45 is a block diagram of a digital multimeter with a display thatcan change color in accordance with measurement quantity.

FIG. 46 is a block diagram of a digital multimeter with a display thatcan change color in accordance with measurement location.

FIG. 47 is a simplified schematic diagram of a variable color digitalmultimeter for measuring outputs of different transducers.

FIG. 48 is a simplified schematic diagram of a variable color digitalmultimeter for measuring signals from different locations.

FIG. 49 is a simplified schematic diagram of a variable color digitalmultimeter for measuring signals by different methods.

FIG. 50 is a simplified schematic diagram of a variable color digitalthermometer.

FIG. 51 is a simplified schematic diagram of a digital ampermeter withvariable color range indication.

FIG. 52 is a simplified schematic diagram of a digital voltmeter withvariable color range indication.

FIG. 53 is a simplified schematic diagram of a digital ohmmeter withvariable color range indication.

FIG. 54 is a detail of the multimeter shown in FIGS. 51, 52, and 53.

FIG. 55 is a simplified schematic diagram of a digital voltmeter fordisplaying positive and negative measurement results in respectivelydifferent colors.

FIG. 56 is a simplified schematic diagram of a variable color displaysystem for displaying decimal numbers such that digits preceding andfollowing the decimal point are displayed in respectively differentcolors.

FIG. 57 is a timing diagram of the circuit shown in FIG. 56.

FIG. 58 is a simplified schematic diagram of a variable color displaysystem for displaying integers and decimal numbers in respectivelydifferent colors.

FIG. 59 is a block diagram of a variable color display device forselectively displaying output digital data from different digitaldevices in respectively different colors.

FIG. 60 is a simplified schematic diagram of a variable color digitalbarometer.

FIG. 61 is a simplified schematic diagram of a digital multimeter fordisplaying measurement results in accordance with time.

FIG. 62 is a block diagram of a variable color digital multimeter withcomparator and memory.

FIG. 63 is a block diagram of a variable color digital multimeter withcomparator and memory for high and low limits.

FIG. 64 is a block diagram of a variable color digital multimeter withcomparator and memory for previous measurement values.

FIG. 65 is a block diagram of a variable color digital multimeter withmemory for previous measurement errors.

FIG. 66 is a schematic diagram of a comparator with low and highmeasurement limits.

FIG. 67 is a schematic diagram of a comparator and error counter.

FIG. 68 is a detail of the comparator, error flip-flop, and colorcontrol combination.

FIG. 69 is a detail of the comparator, error memory, and color convertercombination.

FIG. 70 is a detail of the low measurement limit memory and comparatorcombination.

FIG. 71 is a detail of the error counter and PROM combination.

FIG. 72 is a schematic diagram of a variable color digital multimeterwith registered comparator for comparing instant measured values withpreviously stored ones.

FIG. 73 is a block diagram of a variable color digital multimeter withuniform color control for all display digits.

FIG. 74 is a block diagram of a variable color digital multimeter withindependent color control for each display digit.

FIG. 75 is a block diagram of a dual digital voltmeter with singlevariable color digital display.

FIG. 76 is a block diagram of a variable color RMS digital voltmeterwith variable color crest factor indication.

FIG. 77 is the RMS and crest factor chart.

FIG. 78 is an expanded block diagram of a crest factor converter withratio producing circuit.

FIG. 79 is an expanded block diagram of a crest factor converter withprecision divider.

FIG. 80 is a schematic diagram of an RMS-to-DC converter.

FIG. 81 is a schematic diagram of a peak detector.

FIG. 82 is an expanded block diagram of 2-primary color control for thecrest factor converter.

FIG. 83 is an expanded block diagram of 3-primary color control for thecrest factor converter.

FIG. 84 is an expanded block diagram of 2-primary color converter forthe crest factor converter.

FIG. 85 is an expanded block diagram of 3-primary color converter forthe crest factor converter.

FIG. 86 is a front view of a variable color digital multimeter of thepresent invention.

FIG. 87 is a block diagram of a variable color digital multimetercontrolled by a microprocessor.

FIG. 88 is an expanded block diagram of a variable color digitalmultimeter for indicating front and rear measurements in differentcolors.

FIG. 89 is an expanded block diagram of a variable color digitalmultimeter for indicating DC, AC, and OHMS measurements in respectivelydifferent colors.

FIG. 90 is an expanded block diagram of a variable color digitalmultimeter for indicating measurements with filter and without filter indifferent colors.

Throughout the drawings, like characters indicate like parts.

BRIEF DESCRIPTION OF THE TABLES

In the tables which show examples of the relationship between an inputvoltage, memory contents, and resulting color in the color converter ofthe present invention,

TABLE 1 shows the characteristic of a step variable 2-primary colorconverter.

TABLE 2 shows a rainbow-like characteristic of a continuously variable3-primary color converter.

Throughout the tables, memory addresses and data are expressed in a wellknown hexadecimal notation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now, more particularly, to the drawings, in FIG. 1 is shown ablock diagram of a typical prior art digital display system whichusually includes a device 10 a for developing digital data, a suitabledecoder 20 for converting the digital data into a displayable code, anda monochromatic digital display 30 for indicating the digital datavisually.

As shown in FIG. 2, the present invention resides in the substitution ofa commercially well known monochromatic digital display with a variablecolor digital display 40, and in the addition of a color control circuit50 for controlling the color of display 40. The variable color digitaldisplay system of this invention can simultaneously indicate the valuesof two different quantities, from the outputs of respective devices 10b, 10 c, by causing the value of the first quantity to be indicated ondisplay 40 in digital format, and by controlling the color of display 40in accordance with the value of the second quantity.

In FIG. 3 is shown a block diagram of another embodiment of a variablecolor digital display system of the present invention, characterized bya step variable color control circuit 51.

In FIG. 4 is shown a block diagram of still another embodiment ofvariable color digital display system, characterized by a continuouslyvariable color control circuit 56.

In FIG. 5 is shown a block diagram of a 2-primary color display systemincluding a commercially well known 7-segment display decoder driver 22,a variable color 7-segment display element 42, and a 2-primary colorcontrol logic circuit 52. The decoder driver 22 accepts a 4-bit BCD(binary coded decimal) code at its inputs A0, A1, A2, A3 and developsoutput drive signals at its outputs a, b, c, d, e, f, g, and DP (decimalpoint) to drive respective segments of 7-segment display element 42. Thecolor control circuit 52 accepts color control logic signals at itsinputs R (red), Y (yellow), and G (green) and develops at its outputsdrive signals for red bus 5 and green bus 6, respectively, to illuminatedisplay element 42 in a selected color.

In FIG. 6 is shown a block diagram of a 3-primary color display systemincluding a 7-segment display decoder driver 22, variable color7-segment display element 43, and a 3-primary color control logiccircuit 53. The color control circuit 53 accepts color control logicsignals at its inputs R (red), Y (yellow), G (green), BG (blue-green), B(blue), P (purple), and W (white) and develops at its outputs drivesignals for red bus 5, green bus 6, and blue bus 7, respectively, toilluminate display element 43 in a selected color.

In FIG. 7, the 2-primary color display element includes seven elongateddisplay segments a, b, c, d, e, f, and g, arranged in a conventionalpattern, which may be selectively energized in different combinations todisplay the desired digits. Each display segment includes a pair of LEDs(light emitting diodes): red LED 2 and green LED 3, which are closelyadjacent such that the light signals emitted therefrom are substantiallysuperimposed upon each other to mix the colors. To facilitate theillustration, the LEDs are designated by segment symbols, e.g., the redLED in the segment a is designated as 2 a, etc.

In FIG. 8, red LED 2 e and green LED 3 e are placed on the base of asegment body 15 a which is filled with a transparent light scatteringmaterial 16. When forwardly biased, LEDs 2 e and 3 e emit light signalsof red and green colors, respectively, which are scattered withintransparent material 16, thereby blending the red and green lightsignals into a composite light signal that emerges at the upper surfaceof segment body 15 a. The color of the composite light signal may becontrolled by varying the portions of the red and green light signals.

In FIG. 9, each display segment of the 3-primary color display elementincludes a triad of LEDs: red LED 2, green LED 3, and blue LED 4, whichare closely adjacent such that the light signals emitted therefrom aresubstantially superimposed upon one another to mix the colors.

In FIG. 10, red LED 2 e, green LED 3 e, and blue LED 4 e are placed onthe base of a segment body 15 b which is filled with a transparent lightscattering material 16. Red LEDs are typically manufactured by diffusinga p-n junction into a GaAsP epitaxial layer on a GaAs substrate; greenLEDs typically use a GaP epitaxial layer on a GaP substrate; blue LEDsare typically made from SiC material.

When forwardly biased, LEDs 2 e, 3 e, and 4 e emit light signals of red,green, and blue colors, respectively, which are scattered withintransparent material 16, thereby blending the red, green, and blue lightsignals into a composite light signal that emerges at the upper surfaceof segment body 15 b. The color of the composite light signal may becontrolled by varying the portions of the red, green, and blue lightsignals.

Tn FIG. 11 is shown a schematic diagram of a 2-primary color commoncathodes 7-segment display element 42 which can selectively displayvarious digital fonts in different colors on display segments a, b, c,d, e, f, g, and DP (Decimal Point). The anodes of all red and green LEDpairs are interconnected in each display segment and are electricallyconnected to respective outputs of a commercially well knowncommon-cathode 7-segment decoder driver 23. The cathodes of all red LEDs2 a, 2 b, 2 c, 2 d, 2 e, 2 f, 2 g, and 2 i are interconnected to acommon electric path referred to as a red bus 5. The cathodes of allgreen LEDs 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, 3 g, and 3 i are interconnectedto a like common electric path referred to as a green bus 6.

The red bus 5 is connected to the output of a tri-state inverting buffer63 a, capable of sinking sufficient current to forwardly bias all redLEDs 2 a to 2 i in display element 42. The green bus 6 is connected tothe output of a like buffer 63 b. The two buffers 63 a, 63 b can besimultaneously enabled by applying a low logic level signal to the inputof inverter 64 a, and disabled by applying a high logic level signalthereto. When buffers 63 a, 63 b are enabled, the conditions of red bus5 and green bus 6 can be selectively controlled by applying suitablelogic control signals to the bus control inputs RB (red bus) and GB(green bus), to illuminate display element 42 in a selected color. Whenthe buffers 63 a, 63 b are disabled, both red bus 5 and green bus 6 areeffectively disconnected to cause display element 42 to be completelyextinguished.

In FIG. 12 is shown a schematic diagram of a 3-primary color commonanodes 7-segment display element 43 which can selectively displaydigital fonts in different colors. The cathodes of all red, green, andblue LED triads in each display segment are interconnected andelectrically connected to respective outputs of a commercially wellknown common anode 7-segment decoder driver 24. The anodes of all redLEDs 2 a, 2 b, 2 c, 2 d, 2 e, 2 f, and 2 g are interconnected to form acommon electric path referred to as a red bus 5. The anodes of all greenLEDs 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, and 3 g are interconnected to form alike common electric path referred to as a green bus 6. The anodes ofall blue LEDs 4 a, 4 b, 4 c, 4 d, 4 e, 4 f, and 4 g are interconnectedto form a like common electric path referred to as a blue bus 7.

The red bus 5 is connected to the output of a non-inverting tri-statebuffer 62 a, capable of sourcing sufficient current to illuminate allred LEDs 2 a to 2 g in display element 43. The green bus 6 is connectedto the output of a like buffer 62 b. The blue bus 7 is connected to theoutput of a like buffer 62 c. The three buffers 62 a, 62 b, and 62 c canbe simultaneously enabled, by applying a low logic level signal to theinput of inverter 64 b, and disabled by applying a high logic levelsignal thereto. When buffers 62 a, 62 b, and 62 c are enabled, theconditions of red bus 5, green bus 6, and blue bus 7 can be selectivelycontrolled by applying valid combinations of logic level signals to thebus control inputs RB (red bus), GB (green bus), and BB (blue bus), toilluminate display element 43 in a selected color. When buffers 62 a, 62b, and 62 c are disabled, red bus 5, green bus 6, and blue bus 7 areeffectively disconnected to cause display element 43 to be completelyextinguished.

Step Variable Color Control

In FIG. 13 is shown a logic circuit 69 a for developing drive signalsfor red bus 5 and green bus 6, to control the color of display element42 shown in FIG. 11. Two voltage levels, referred to as logic high andlow, are used throughout the description of the digital circuits. Thecolor of display element 42 may be controlled by applying validcombinations of logic level signals to its color control inputs R (red),Y (yellow), and G (green). The logic circuit 69 a combines the inputsignals in a logic fashion and develops output drive signals RB (redbus) and GB (green bus), for activating red bus 5 and green bus 6,respectively, of display element 42.

In FIG. 14 is shown a like logic circuit 69 b for developing drivesignals for red bus 5, green bus 6, and blue bus 7, to control the colorof display element 43 shown in FIG. 12. The color of display element 43may be controlled by applying valid combinations of logic level signalsto its color control inputs B (blue), P (purple), BG (blue-green), G(green), Y (yellow), W (white), and R (red). The logic circuit 69 bcombines the input signals in a logic fashion and develops output drivesignals RB (red bus), GB (green bus), and BB (blue bus), for activatingred bus 5, green bus 6, and blue bus 7, respectively, of display element43.

Exemplary schematic diagrams of the color control logic circuits shownin FIGS. 15 and 16 consider active high logic levels, which means thatonly the selected color control input is maintained at a high logiclevel, while all remaining color control inputs are maintained at a lowlogic level. The circuit in FIG. 15 is a detail of the color controllogic circuit 69 a employing 2-input logic OR gates 60 a and 60 b,interposed between the color control inputs R, Y, G and bus controloutputs RB, GB, in a manner which will become more apparent from thedescription below. A like circuit in FIG. 16 is a detail of the colorcontrol logic circuit 69 b employing 4-input logic OR gates 61 a, 61 b,and 61 c similarly interposed between the color control inputs B, P, BG,G, Y, W, R and bus control outputs RB, GB, BB. It will be obvious tothose skilled in the art that other types of logic devices may beeffectively used.

The operation of display element 42 shown in FIG. 11 will be nowexplained by the example of illuminating a digit ‘7’ in three differentcolors. A simplified schematic diagram to facilitate the explanation isshown in FIG. 17. Any digit between 0 and 9 can be selectively displayedby applying the appropriate BCD code to the inputs A0, A1, A2, and A3 ofcommon-cathode 7-segment decoder driver 23. The decoder driver 23develops at its outputs a, b, c, d, e, f, g, and DP drive signals forenergizing selected groups of the segments to thereby visually displaythe selected number, in a manner well known to those having ordinaryskill in the art. To display decimal number ‘7’, a BCD code 0111 isapplied to the inputs A0, A1, A2, and A3. The decoder driver 23 developshigh voltage levels at its outputs a, b, and c, to illuminate equallydesignated segments a, b, and c, and low voltage levels at all remainingoutputs (not shown), to extinguish all remaining segments d, e, f, andg.

To illuminate display element 42 in red color, the color control input Ris raised to a high logic level, and the color control inputs Y and Gare maintained at a low logic level. As a result, the output of OR gate60 a rises to a high logic level, thereby causing the output of buffer63 a to drop to a low logic level. The current flows from the output aof decoder driver 23, via red LED 2 a and red bus 5, to current sinkingoutput of buffer 63 a. Similarly, the current flows from the output b ofdecoder driver 23, via red LED 2 b and red bus 5, to the output ofbuffer 63 a. The current flows from the output c of decoder driver 23,via red LED 2 c and red bus 5, to the output of buffer 63 a. As aresult, segments a, b, and c illuminate in red color, thereby causing avisual impression of a character ‘7’. The green LEDs 3 a, 3 b, 3 cremain extinguished because the output of buffer 63 b is at a high logiclevel, thereby disabling green bus 6.

To illuminate display element 42 in green color, the color control inputG is raised to a high logic level, while the color control inputs R andY are maintained at a low logic level. As a result, the output of ORgate 60 b rises to a high logic level, thereby causing the output ofbuffer 63 b to drop to a low logic level. The current flows from theoutput a of decoder driver 23, via green LED 3 a and green bus 6, tocurrent sinking output of buffer 63 b. Similarly, the current flows fromthe output b of decoder driver 23, via green LED 3 b and green bus 6, tothe output of buffer 63 b. The current flows from the output c ofdecoder driver 23, via green LED 3 c and green bus 6, to the output ofbuffer 63 b. As a result, segments a, b, and c illuminate in greencolor. The red LEDs 2 a, 2 b, and 2 c remain extinguished because theoutput of buffer 63 a is at a high logic level, thereby disabling redbus 5.

To illuminate display element 42 in yellow color, the color controlinput Y is raised to a high logic level, while the color inputs R and Gare maintained at a low logic level. As a result, the outputs of both ORgates 60 a and 60 b rise to a high logic level, thereby causing theoutputs of both buffers 63 a and 63 b to drop to a low logic level. Thecurrent flows from the output a of decoder driver 23, via red LED 2 aand red bus 5, to current sinking output of buffer 63 a, and, via greenLED 3 a and green bus 6, to current sinking output of buffer 63 b.Similarly, the current flows from the output b of decoder driver 23, viared LED 2 b and red bus 5, to the output of buffer 63 a, and, via greenLED 3 b and green bus 6, to the output of buffer 63 b. The current flowsfrom the output c of decoder driver 23, via red LED 2 c and red bus 5,to the output of buffer 63 a, and, via green LED 3 c and green bus 6, tothe output of buffer 63 b. As a result of blending light of red andgreen colors in each segment, segments a, b, and c illuminate insubstantially yellow color.

The operation of display element 43 shown in FIG. 12 will be nowexplained by the example of illuminating a digit ‘1’ in seven differentcolors. A simplified schematic diagram to facilitate the explanation isshown in FIG. 18. To display decimal number ‘1’, a BCD code 0001 isapplied to the inputs A0, A1, A2, and A3 of common anode 7-segmentdecoder driver 24. The decoder driver 24 develops low voltage levels atits outputs b and c, to illuminate equally designated segments b and c,and high voltage levels at all remaining outputs (not shown), toextinguish all remaining segments a, d, e, f, and g.

To illuminate display element 43 in red color, the color control input Ris raised to a high logic level, while all remaining color controlinputs are maintained at a low logic level. As a result, the output ofOR gate 61 a rises to a high logic level, thereby causing the output ofbuffer 62 a to rise to a high logic level. Then current flows from theoutput of buffer 62 a, via red bus 5 and red LED 2 b, to the output b ofdecoder driver 24, and, via red LED 2 c, to the output c of decoderdriver 24. As a result, segments b and c illuminate in red color,thereby causing a visual impression of a character ‘1’. The green LEDs 3b, 3 c and blue LEDs 4 b, 4 c remain extinguished because green bus 6and blue bus 7 are disabled.

To illuminate display element 43 in green color, the color control inputG is raised to a high logic level, while all remaining color controlinputs are maintained at a low logic level. As a result, the output ofOR gate 61 b rises to a high logic level, thereby causing the output ofbuffer 62 b to rise to a high logic level. The current flows from theoutput of buffer 62 b, via green bus 6 and green LED 3 b, to the outputb of decoder driver 24, and, via green LED 3 c, to the output c ofdecoder driver 24. As a result, segments b and c illuminate in greencolor.

To illuminate display element 43 in blue color, the color control inputB is raised to a high logic level, while all remaining color controlinputs are maintained at a low logic level. As a result, the output ofOR gate 61 c rises to a high logic level, thereby causing the output ofbuffer 62 c to rise to a high logic level. The current flows from theoutput of buffer 62 c, via blue bus 7 and blue LED 4 b, to the output bof decoder driver 24, and, via blue LED 4 c, to the output c of decoderdriver 24. As a result, segments b and c illuminate in blue color.

To illuminate display element 43 in yellow color, the color controlinput Y is raised to a high logic level, while all remaining colorcontrol inputs are maintained at a low logic level. As a result, theoutputs of OR gates 61 a and 61 b rise to a high logic level, therebycausing the outputs of buffers 62 a and 62 b to rise to a high logiclevel. The current flows from the output of buffer 62 a, via red bus 5and red LED 2 b, to the output b of decoder driver 24, and, via red LED2 c, to the output c of decoder driver 24. The current also flows fromthe output of buffer 62 b, via green bus 6 and green LED 3 b, to theoutput b of decoder driver 24, and, via green LED 3 c, to the output cof decoder driver 24. As a result of blending light of red and greencolors in each segment, the segments b and c illuminate in substantiallyyellow color.

To illuminate display element 43 in purple color, the color controlinput P is raised to a high logic level, while all remaining colorcontrol inputs are maintained at a low logic level. As a result, theoutputs of OR gates 61 a and 61 c rise to a high logic level, therebycausing the outputs of buffers 62 a and 62 c to rise to a high logiclevel. The current flows from the output of buffer 62 a, via red bus 5and red LED 2 b, to the output b of decoder driver 24, and, via red LED2 c, to the output c of decoder driver 24. The current also flows fromthe output of buffer 62 c, via blue bus 7 and blue LED 4 b, to theoutput b of decoder driver 24, and, via blue LED 4 c, to the output c ofdecoder driver 24. As a result of blending light of red and blue colorsin each segment, segments b and c illuminate in substantially purplecolor.

To illuminate display element 43 in blue-green color, the color controlinput BG is raised to a high logic level, while all remaining colorcontrol inputs are maintained at a low logic level. As a result, theoutputs of OR gates 61 b and 61 c rise to a high logic level, therebycausing the outputs of buffers 62 b and 62 c to rise to a high logiclevel. The current flows from the output of buffer 62 b, via green bus 6and green LED 3 b, to the output b of decoder driver 24, and, via greenLED 3 c, to the output c of decoder driver 24. The current also flowsfrom the output of buffer 62 c, via blue bus 7 and blue LED 4 b, to theoutput b of decoder driver 24, and, via blue LED 4 c, to the output c ofdecoder driver 24. As a result of blending light of green and bluecolors in each segment, segments b and c illuminate in substantiallyblue-green color.

To illuminate display element 43 in white color, the color control inputW is raised to a high logic level, while all remaining color controlinputs are maintained at a low logic level. As a result, the outputs ofOR gates 61 a, 61 b, and 61 c rise to a high logic level, therebycausing the outputs of respective buffers 62 a, 62 b, and 62 c to riseto a high logic level. The current flows from the output of buffer 62 a,via red bus 5 and red LED 2 b, to the output b of decoder driver 24,and, via red LED 2 c, to the output c of decoder driver 24. The currentalso flows from the output of buffer 62 b, via green bus 6 and green LED3 b, to the output b of decoder driver 24, and, via green LED 3 c, tothe output c of decoder driver 24. The current also flows from theoutput of buffer 62 c, via blue bus 7 and blue LED 4 b, to the output bof decoder driver 24, and, via blue LED 4 c, to the output c of decoderdriver 24. As a result of blending light of red, green, and blue colorsin each segment, segments b and c illuminate in substantially whitecolor.

Since the outputs of decoder driver 24 may be overloaded by driving atriad of LEDs in parallel in display element 43, rather than a singleLED in a monochromatic display, it would be obvious to employ suitablebuffers to drive respective color display segments (not shown).

To illustrate how the present invention can be utilized in amulti-element variable color display configuration, in FIG. 19 is showna detail of the interconnection in a 2-primary color 4-digit displayhaving display segments 1 a, 1 b, 1 c, and 1 d arranged in a 7-segmentfont. The color control inputs R, Y, and G of color controls 52 a, 52 b,52 c, and 52 d of all display elements 46 a, 46 b, 46 c, and 46 d areinterconnected, respectively, and enable inputs E1, E2, E3, and E4 areused to control the conditions of respective display elements 46 a, 46b, 46 c, and 46 d. A high logic level at the enable input E extinguishesthe particular display element 46 a, 46 b, 46 c, or 46 d; a low logiclevel therein illuminates display element 46 a, 46 b, 46 c, or 46 d in acolor determined by the instant conditions of the color control inputsR, Y, and G.

In FIG. 20 is shown a like detail of the interconnection in a 3-primarycolor 4-digit display having display segments 1 a, 1 b, 1 c, and 1 darranged in a 7-segment font. Similarly, the color control inputs B, P,BC, G, Y, W, and R of color controls 53 a, 53 b, 53 c, and 53 d of alldisplay elements 47 a, 47 b, 47 c, and 47 d are interconnected, and theconditions of respective display elements 47 a, 47 b, 47 c, and 47 d arecontrolled by enable inputs E1, E2, E3, and E4. A high logic level atthe enable input E extinguishes the particular display element 47 a, 47b, 47 c, or 47 d; a low logic level therein illuminates display element47 a, 47 b, 47 c, or 47 d in a color determined by the instantconditions of the color control inputs B, P, BG, G, Y, W, and R.

The exemplary color control circuits described herein will cooperateequally well with a multi-element variable color display constructedeither in common cathodes or in common anodes configuration.

The enable inputs E1, E2, E3, E4 may be utilized to control the variablecolor multi-digit display in a multiplexed configuration, wherein thecolor codes for the display digits are presented in a sequence, one at atime, at a relatively fast rate, while the particular display digit isenabled.

In FIG. 21 is shown a block diagram of a signal converter for developingcolor control logic signals for 2-primary color display. The signalconverter 85 a accepts at its input voltage from a variable analogvoltage source 11 and develops at its outputs color control logicsignals R, Y, G, having relation to the magnitude of instant inputanalog voltage, for controlling the color of variable color displayelement 42, shown in FIGS. 11 and 15, in accordance with the magnitudeof input voltage.

In FIG. 22 is shown a block diagram of a like signal converter fordeveloping color control logic signals for 3-primary color display. Thesignal converter 85 b accepts at its inputs voltage from source 11 anddevelops output color control logic signals B, P, BG, G, Y, W, R,related to the magnitude of instant input analog voltage, forcontrolling the color of variable color display element 43, shown inFIGS. 12 and 16, in accordance with the magnitude of input voltage.

In FIG. 23, the output voltage of variable analog voltage source 11 isapplied to interconnected inputs of two analog comparators 82 a, 82 b,in a classic ‘window’ comparator configuration. When the voltagedeveloped by source 11 is lower than the low voltage limit Vlo, set by apotentiometer 92 a, the output of comparator 82 a drops to a low logiclevel, thereby forcing the output of inverter 65 a to rise to a highlogic level, to activate the color control logic input Y, to therebyilluminate display element 42, shown in FIGS. 11 and 15, in yellowcolor.

When the voltage developed by source 11 is higher than the high voltagelimit Vhi, set by a potentiometer 92 b, the output of comparator 82 bdrops to a low logic level, thereby forcing the output of inverter 65 bto rise to a high logic level, to activate the color control logic inputR, to thereby illuminate display element 42 in red color.

When the voltage developed by source 11 is between the low voltage limitVlo and high voltage limit Vhi, the outputs of comparators 82 a, 82 brise to a high logic level, thereby causing the output of AND gate 66 torise to a high logic level, to activate the color control logic input G,to thereby illuminate display element 42 in green color.

FIG. 24 is a graph depicting the relationship between the input voltageof the comparator circuit shown in FIG. 23 and the color of the displayelement shown in FIG. 11. The display element illuminates in yellowcolor for the input voltage lower than the limit Vlo, in green color forthe input voltage between the limits Vlo and Vhi, and in red color forthe input voltage higher than the limit Vhi.

In FIG. 25, the output voltage of variable analog voltage source 11 isapplied to interconnected ‘+’ inputs of six analog comparators 82 c, 82d, 82 e, 82 f, 82 g, 82 h, connected in a well known ‘multiple aperturewindow’ configuration. There are six progressively increasing voltagelimits V1 to V6, set by respective potentiometers 92 c to 92 h. Theoutputs of comparators 82 c to 82 h are respectively connected, viainverters 65 c to 65 h, to the inputs I1 to I7 of a priority encoder 67.Each of the inputs I1 to I7 has assigned a certain priority (from I1being the lowest priority progressively to I7 being the highest one).The priority encoder 67 develops at its outputs 00, 01, 02 a codeidentifying the highest priority input activated. The outputs of encoder67 are respectively connected, via inverters 65 j to 65 m, to the inputsA0, A1, A2 of a 3-to-8 line decoder 68, to decode the outputs of encoder67 into seven mutually exclusive active logic low outputs Y1 to Y7. Theoutputs Y1 to Y7 are respectively connected, via inverters 65 p to 65 v,to the color control logic inputs B, P, BG, G, Y, W, R of displayelement 43 shown in FIGS. 12 and 16.

When the output voltage of source 11 is lower than the lowest voltagelimit V1, the output of comparator 82 c drops to a low logic level,thereby activating the input I1 of priority encoder 67. The code 110developed at the outputs 00, 01, 02 is inverted by inverters 65 j to 65m to yield the code 001 which produces a low logic level at the outputY1, to force, via inverter 65 p, the color control input B to a highlogic level for causing display element 43 to illuminate in blue color.

When the output voltage of the source 11 is between the adjacent voltagelimits, e.g., V4 and V5, the output of comparator 82 f rises to a highlogic level, thereby activating the input I5 of priority encoder 67. Thecode 100 developed at the inputs of decoder 68 produces a high logiclevel at the color control logic input Y, and display element 43illuminates in yellow color.

FIG. 26 is a graph depicting the relationship between the input voltageof the comparator circuit shown in FIG. 25 and the color of displayelement 42 shown in FIG. 12. The display element illuminates in bluecolor for the input voltage lower than the limit V1, in purple color forthe input voltage between the limits V1 and V2, in blue-green color forthe input voltage between the limits V2 and V3, in green color for theinput voltage between the limits V3 and V4, in yellow color for theinput voltage between the limits V4 and V5, in white color for the inputvoltage between the limits V5 and V6, and in red color for the inputvoltage higher than the limit V6.

It would be obvious to those having ordinary skill in the art, in theview of this disclosure, that the color sequences could be readilychanged by differently interconnecting the outputs of the comparatorcircuit with the color control logic inputs of display element 43.

Continuously Variable Color Converter

FIG. 27 is a block diagram of a 2-LED continuously variable colordisplay system, which includes a device 10 for developing electricsignals and 2-LED color converter 57 for controlling red bus 5 and greenbus 6, respectively, of 2-LED variable color display element 42 inaccordance with the electric signals.

FIG. 28 is a block diagram of a 3-LED continuously variable colordisplay system which differs from the like system shown in FIG. 27 inthat a 3-LED color converter circuit 58 is utilized to control red bus5, green bus 6, and blue bus 7, respectively, of 3-LED variable colordisplay element 43, in accordance with the electric signals developed bydevice 10.

The display system shown in FIG. 29 utilizes a scaling circuit 80 awhich scales input analog voltage levels to a voltage range suitable foran A/D converter 74 a, which in turn develops at its outputs a digitalcode having relation to the value of the input analog voltage. Theoutput lines of A/D converter 74 a are connected to the address inputsof a memory 76 having a plurality of addressable locations which containdata indicating the portions of red color for several different valuesof the input analog voltage. The output data of memory 76 are applied tothe inputs of a color converter 57 which will develop control signalsfor red bus 5 and green bus 6, respectively, of variable color displayelement 42.

The display system shown in FIG. 30 utilizes a scaling circuit 80 b andan A/D converter 74 b for converting the instant value of an inputanalog voltage to a digital code. The outputs of A/D converter 74 b areconnected, in parallel, to the address inputs of memory 76 a, whichcontains data indicating the portions of red color, to the addressinputs of memory 76 b, which contains data indicating the portions ofgreen color, and to the address inputs of memory 76 c, which containsdata indicating the portions of blue color. The output data of memory 76a are applied to red color converter 59 a which will develop controlsignals for red bus 5 of variable color display element 43. The outputdata of memory 76 b are applied to green color converter 59 b which willdevelop control signals for green bus 6 of display element 43. Theoutput data of memory 76 c are applied to blue color converter 59 cwhich will develop control signals for blue bus 7 of display element 43.

FIG. 31 is a schematic diagram of a scaling circuit capable of shiftingand amplifying the input voltage levels. The circuit utilizes twooperational amplifiers 81 a and 81 b in a standard invertingconfiguration. The amplifier 81 a is set for a unity gain by usingresistors 90 a and 90 b of equal values; potentiometer 92 a is adjustedto set a desired offset voltage. The amplifier 81 b sets the gain byadjusting feedback potentiometer 92 b to a desired value with respect toresistor 90 c. As a result, an input voltage, which may vary betweenarbitrary limits Vlow and Vhigh, may be scaled and shifted to the rangebetween 0 Volts and 9.961 Volts, to facilitate the use of a commerciallyavailable A/D converter.

FIG. 32 is a schematic diagram of an A/D (analog-to-digital) converter75 which is capable of converting input analog voltage, applied viaresistor 90 e to its input Vin, to 8-bit digital data for addressing amemory 77. The conversion may be initiated from time to time by applyinga short positive pulse 99 a to the Blank and Convert input B&C. A/Dconverter 75 will thereafter perform a conversion of the instant inputvoltage to 8-bit data indicative of its value. When the conversion iscompleted, the Data Ready output DR drops to a low logic level, therebyindicating that the data are available at the outputs Bit 1 to Bit 8,which are directly connected to respective address inputs A0 to A7 ofmemory 77. When the DR output drops to a low logic level, the ChipSelect input CS of memory 77 is activated, memory 77 is enabled, and thedata, residing at the address selected by the instant output of A/Dconverter 75, will appear at its data outputs D0 to D7.

The description of the schematic diagram in FIG. 33 should be consideredtogether with its accompanying timing diagram shown in FIG. 34. A clocksignal 99 b of a suitable frequency (e.g., 10 kHz), to provide aflicker-free display, is applied to the Clock Pulse inputs CP of 8-bitbinary counters 71 e and 71 f to step them down. At the end of eachcounter cycle, which takes 256 clock cycles to complete, the TerminalCount output TC of counter 71 e drops to a low logic level for one clockcycle, to thereby indicate that the lowest count was reached. Thenegative pulse 99 c at the TC output of counter 71 e, which is connectedto the Parallel Load input PL of counter 71 f, causes the instant dataat the outputs of memory 76 to be loaded into counter 71 f. The data atmemory 76 represent the portion of red color; the portion of green coloris complementary. The rising edge of the TC pulse 99 c triggersflip-flop 73 into its set condition wherein its output Q rises to a highlogic level.

The counter 71 f will count down, from the loaded value, until itreaches zero count, at which moment its TC output drops to a low logiclevel. The negative pulse at the TC output of counter 71 f, which isconnected to the Clear Direct input CD of flip-flop 73, causes thelatter to be reset and to remain in its reset condition until it is setagain at the beginning of the next 256-count cycle. It is thus obviousthat the Q output of flip-flop 73 is at a high logic level for a periodof time proportional to the data initially loaded into counter 71 f. Thecomplementary output {overscore (Q)} a high logic level for acomplementary period of time.

The Q and {overscore (Q)} outputs of flip-flop 73 are connected to redbus 5 and green bus 6, respectively, via suitable buffers 63 a and 63 b,shown in detail in FIG. 11, to respectively energize red bus 5 and greenbus 6 for variable time periods, depending on the data stored in memory76.

By referring now, more particularly, to the timing diagram shown in FIG.34, in which the waveforms are compressed to facilitate theillustration, the EXAMPLE 1 considers the memory data ‘FD’, in astandard hexadecimal notation, to generate light of substantially redcolor. At the beginning of the counter cycle, pulse 99 c loads data ‘FD’into counter 71 f. Simultaneously, flip-flop 73 is set by the risingedge of pulse 99 c. The counter 71 f will be thereafter stepped down byclock pulses 99 b, until it reaches zero count, 2 clock cycles beforethe end of the counter cycle. At that instant a short negative pulse 99d is produced at its output TC to reset flip-flop 73, which will remainreset for 2 clock cycles and will be set again by pulse 99 c at thebeginning of the next counter cycle, which will repeat the process. Itis readily apparent that flip-flop 73 was set for 254 clock cycles, orabout 99% of the time, and reset for 2 clock cycles, or about 1% of thetime. Accordingly, red bus 5 of display element 42 is energized forabout 99% of the time, and green bus 6 is energized for the remainingabout 1% of the time. As a result, display element 42 illuminates insubstantially red color.

The EXAMPLE 2 considers the memory data ‘02’ (HEX) to generate light ofsubstantially green color. At the beginning of the counter cycle, data‘02’ are loaded into counter 71 f, and, simultaneously, flip-flop 73 isset. The counter 71 f will count down and will reach zero count after 2clock cycles. At that instant it produces at its output TC a negativepulse 99 e to reset flip-flop 73. It is readily apparent that flip-flop73 was set for 2 clock cycles, or about 1% of the time, and reset for254 clock cycles, or about 99% of the time. Accordingly, red bus 5 ofdisplay element 42 is energized for about 1% of the time, and green bus6 is energized for the remaining about 99% of the time. As a result,display element 42 illuminates in substantially green color.

The EXAMPLE 3 considers the memory data ‘80’ (HEX) to generate light ofsubstantially yellow color. At the beginning of the counter cycle, data‘80’ are loaded into counter 71 f, and, simultaneously, flip-flop 73 isset. The counter 71 f will count down and will reach zero count after128 clock cycles. At that instant it produces at its output TC anegative pulse 99 f to reset flip-flop 73. It is readily apparent thatflip-flop 73 was set for 128 clock cycles, or about 50% of the time, andreset for 128 clock cycles, or about 50% of the time. Accordingly, redbus 5 of display element 42 is energized for about 50% of the time, andgreen bus 6 is energized for the remaining about 50% of the time. As aresult of blending substantially equal portions of red and green colors,display element 42 illuminates in substantially yellow color.

The description of the schematic diagram of a 3-LED color converter inFIG. 35 should be considered together with its accompanying timingdiagrams shown in FIGS. 36 and 37. A clock signal 99 b is applied to theCP inputs of counters 71 d, 71 a, 71 b, and 71 c to step them down.Every 256 counts a negative pulse 99 c is generated at the TC output ofcounter 71 d, to load data into counters 71 a, 71 b, and 71 c fromrespective memories 76 a, 76 b, and 76 c, and to set flip-flops 73 a, 73b, and 73 c. The data in red memory 76 a represent the portions of redcolor, the data an green memory 76 b represent the portions of greencolor, and the data in blue memory 76 c represent the portions of bluecolor to be blended.

The counters 71 a, 71 b, and 71 c will count down, from the respectiveloaded values, until zero counts are reached. When the respective valuesof the loaded data are different, the length of time of the count-downis different for each counter 71 a, 71 b, and 71 c. When a particularcounter 71 a, 71 b, or 71 c reaches zero count, its TC outputmomentarily drops to a low logic level, to reset its associatedflip-flop (red counter 71 a resets its red flip-flop 73 a, green counter71 b resets its associated green flip-flop 73 b, and blue counter 71 cresets its associated blue flip-flop 73 c). Eventually, all threeflip-flops 73 a, 73 b, and 73 c will be reset. The Q outputs offlip-flops 73 a, 73 b, and 73 c are connected to red bus 5, green bus 6,and blue bus 7, respectively, via suitable buffers 62 a, 62 b, and 62 c,as shown in FIG. 12, to respectively energize red bus 5, green bus 6,and blue bus 7 for variable periods of time.

By referring now more particularly to the timing diagram shown in FIGS.36 and 37, the EXAMPLE 4 considers red memory data ‘80’, green memorydata ‘00’, and blue memory data ‘80’, all in hexadecimal notation, togenerate light of substantially purple color. At the beginning of thecounter cycle, pulse 99 c simultaneously loads data ‘80’ from red memory76 a into red counter 71 a, data ‘00’ from green memory 76 b into greencounter 71 b, and data ‘80’ from blue memory 76 c into blue counter 71c. The counters 71 a, 71 b, and 71 c will be thereafter stepped down.The red counter 71 a will reach its zero count after 128 clock cycles;green counter 71 b will reach its zero count immediately; blue counter71 c will reach its zero count after 128 clock cycles.

It is readily apparent that red flip-flop 73 a was set for 128 clockcycles, or about 50% of the time, green flip-flop 73 b was never set,and blue flip-flop 73 c was set for 128 clock cycles, or about 50% ofthe time. Accordingly, red bus 5 of display element 43 is energized forabout 50% of the time, green bus 6 is never energized, and blue bus 7 isenergized for about 50% of the time. As a result of blendingsubstantially equal portions of red and blue colors, display element 43illuminates in substantially purple color.

The EXAMPLE 5 considers red memory data ‘00’, green memory data ‘80’,and blue memory data ‘80’, to generate light of substantially blue-greencolor. At the beginning of the counter cycle, data ‘00’ are loaded intored counter 71 a, data ‘80’ are loaded into green counter 71 b, and data‘80’ are loaded into blue counter 71 c. The red counter 71 a will reachits zero count immediately, green counter 71 b will reach its zero countafter 128 clock periods, and so will blue counter 71 c.

The red flip-flop 73 a was never set, green flip-flop 73 b was set for128 clock pulses, or about 50% of the time, and so was blue flip-flop 73c. Accordingly, green bus 6 of display element 43 is energized for about50% of the time, and so is blue bus 7. As a result, display element 43illuminates in substantially blue-green color.

The EXAMPLE 6 considers red memory data ‘40’, green memory data ‘40’,and blue memory data ‘80’, to generate light of substantially cyancolor. At the beginning of the counter cycle, the data ‘40’ are loadedinto red counter 71 a, data ‘40’ are loaded into green counter 71 b, anddata ‘80’ are loaded into blue counter 71 c. The red counter 71 a willreach its zero count after 64 clock cycles, and so will green counter 71b. The blue counter 71 c will reach its zero count after 128 clockcycles.

The red flip-flop 73 a was set for 64 clock cycles, or about 25% of thetime, and so was green flip-flop 73 b. The blue flip-flop 73 c was setfor 128 clock cycles, or about 50% of the time. Accordingly, red bus 5and green bus 6 of display element 43 are energized for about 25% of thetime, and blue bus 7 is energized for about 50% of the time. As a resultof blending about 50% of blue color, 25% of red color, and 25% of greencolor, display element 43 illuminates in substantially cyan color.

The EXAMPLE 7 considers red memory data ‘80’, green memory data ‘40’,and blue memory data ‘40 ’, to generate light of substantially magentacolor. At the beginning of the counter cycle, the data ‘80’ are loadedinto red counter 71 a, data ‘40’ are loaded into green counter 71 b, anddata ‘40’0 are loaded into blue counter 71 c. The red counter 71 a willreach its zero count after 128 clock cycles, green counter 71 b willreach its zero count after 64 clock cycles, and so will blue counter 71c.

The red flip-flop 73 a was set for 128 clock cycles, or about 50% of thetime, green flip-flop 73 b and blue flip-flop 73 c were set for 64 clockcycles, or about 25% of the time. Accordingly, red bus 5 of displayelement 43 is energized for about 50% of the time, green bus 6 and bluebus 7 are energized for about 25% of the time. As a result, displayelement 43 illuminates in substantially magenta color.

By referring now more particularly to FIGS. 38 and 39, which are graphicrepresentations of TABLES 1 and 2, respectively, the data at each memoryaddress are digital representation of the portion of the particularprimary color. All examples consider an 8-bit wide PROM (ProgrammableRead Only Memory). However, the principles of the invention could beapplied to other types of memories.

In FIG. 38, RED PORTION indicates the portion of red primary color;GREEN PORTION indicates the portion of green primary color. The REDPORTION for a particular memory address was calculated by dividing theactual value of data residing at that address by the maximum possibledata ‘FF’ (HEX). The GREEN PORTION for the same memory address iscomplementary; it was obtained by subtracting the calculated value ofthe RED PORTION from number 1.0.

In FIG. 38 is shown the characteristic of a 2-primary color converter,defined in TABLE 1, for developing color variable in steps: pure greenfor input voltages less than 0.625 V, substantially yellow for voltagesbetween 1.25 V and 1.875 V, pure red for voltages between 2.5 V and3.125 V, and of intermediate colors therebetween, this sequence beingrepeated three times over the voltage range.

In FIG. 39, RED PORTION indicates the portion of red primary color;GREEN PORTION indicates the portion of green primary color; BLUE PORTIONindicates the portion of blue primary color. The RED PORTION for aparticular memory address was calculated by dividing the value of reddata residing at such address by the maximum possible data ‘FF’ (HEX).Similarly, the GREEN PORTION for that memory address was obtained bydividing the value of green data by ‘FF’ (HEX). The BLUE PORTION wasobtained by dividing the value of blue data by ‘FF’ (HEX).

In FIG. 39 is shown the characteristic of 3-primary color converter,defined in TABLE 2, for developing color continuously variable from purered, through substantially orange and yellow, pure green, pure blue, tosubstantially purple, in a rainbow-like fashion.

In the examples of the characteristics of color converters shown inTABLE 1 and TABLE 2, the data values stored in red memory 76 a, greenmemory 76 b, and blue memory 76 c are so designed that the sums of thered data, green data, and blue data are constant for all memoryaddresses, to provide uniform light intensities for all colors. It isfurther contemplated that data stored in red memory 76 a, green memory76 b, and blue memory 76 c may be modified in order to compensate fordifferent efficiencies of red, green, and blue LEDs. By way of anexample, data values for a low efficiency LED may be proportionallyincremented such that the time of energization is proportionallyincreased, to effectively provide equal luminances for LEDs of unequalefficiencies.

With reference to FIG. 40 there is shown the ICI (InternationalCommittee on Illumination) chromaticity diagram designed to specify aparticular color in terms of x and y coordinates. Pure colors arelocated along the horseshoe-like periphery. Reference numbers along theperiphery indicate wavelength in nanometers. When relative portions ofthree primary colors are known, the color of light produced by blendingtheir emissions can be determined by examining the x and y values of ICIcoordinates.

Digital Multimeter

FIG. 41 is a generalized block diagram of a multimeter with variablecolor digital display which includes a multimeter 101 for measuringvalues of a QUANTITY 1, digital decoder driver 21 for converting theoutput data of multimeter 101 to a displayable code, and variable colordigital display 40 for indicating the measured values in digital format.The invention resides in the addition of a color converter circuit 55for converting values of a QUANTITY 2 to color control signals forcontrolling the color of display 40. The display 40 thus simultaneouslyindicates values of the QUANTITY 1, in digital format, and values of theQUANTITY 2, in variable color.

FIG. 42 is a generalized block diagram of a like multimeter system witha multiplexed variable color digital display 41, which differs from thediagram shown in FIG. 41 in that the multimeter 102 develops at itsoutputs multiplexed signals to directly drive display 41.

A digital multimeter shown in a block diagram configuration in FIG. 43is capable of selectively setting certain of its external controls by anexternal control selector 121 a. The invention resides in the additionof associated color selector 121 b for causing variable color digitaldisplay 40 to illuminate in a color corresponding to the selectedexternal control. The measurements performed with different externalcontrols may be displayed in respectively different colors. Theselectors 121 a, 121 b may include relays, mechanical switches,electronic and optical elements, devices for executing program ofinstructions, and the like. The association between the selectors 121 aand 121 b may be, in its simplest form, a direct coupling, whereby theselector 121 b is always in the same position as the selector 121 a, ora more sophisticated association in space, time, hardware, and software.The external controls may comprise measurement modes, such are local,remote, 2-wire, and 4-wire; measurement functions, such are DC voltage,AC voltage, DC current, AC current, resistance, capacitance, andinductance; measurement ranges for selectively scaling measured signals,and the like.

In FIG. 44 is shown a block diagram of a like digital multimeter capableof selectively setting certain of its internal measurement controls byan internal control selector 121 a. The associated color selector 121 bcauses display 40 to illuminate in a color corresponding to the selectedinternal control, such that the measurements performed with differentinternal controls may be displayed in respectively different colors. Theinternal controls may comprise measurement modifiers, such are single,continuous, synchronous, and asynchronous triggering, sample rate,filter, offset, external reference, and scaling; measurement methods,units, and the like.

FIG. 45 is a block diagram of a digital multimeter with measurementquantity selection. By way of an example, when the quantity selector 121a is in its second position, thereby selecting the QUANTITY 2 to theinput of digital multimeter 103, the associated color selector 121 b isalso in its second position, thereby applying the control voltage to thecolor control input C2, to cause the measured values of the QUANTITY 2to be indicated on display 40 in the color C2. The measurements ofdifferent quantities may be indicated in respectively different colors.

FIG. 46 is a block diagram of a digital multimeter with input locationselection. By way of an example, when the location selector 121 a is inits third position, thereby selecting for the input of multimeter 103signals from the LOCATION 3, the associated color selector 121 b is alsoin its third position, thereby applying the control voltage to the colorcontrol input C3, to cause the measured values from the LOCATION 3 to beindicated on display 40 in the color C3. The measurements from differentlocations may be indicated in respectively different colors.

In FIG. 47 is shown an exemplary simplified schematic diagram of adigital multimeter for selectively measuring values of several differentquantities from outputs of a temperature transducer 172, which convertstemperature to voltage, pressure transducer 173, which convertsatmospheric pressure to voltage, and physiological transducer 174, whichconverts physiological information to voltage. The term transducer, asused throughout the description of the invention, is used in its widestsense so as to include every type of a device for performing aconversion of one form of energy to another. The principles of theinvention may be applied to various displacement, motion, force,pressure, sound, flow, temperature, humidity, weight, magnetic, andphysiological transducers, and the like. When switch 123 g is in itsfirst position, thereby selecting temperature transducer 172, digitalvoltmeter 108 measures the output voltage of transducer 172, which isproportional to ambient temperature, and display 48 indicates themeasured temperature in digital format. The associated switch 123 h isalso in its first position, thereby connecting the control voltage +VCCto the color control input C1 of the color control circuit 42, to causethe display 48 to illuminate in the color C1. When switch 123 g is inits second position, thereby selecting pressure transducer 173, display48 indicates the measured atmospheric pressure in digital format and inthe color C2. When switch 123 g is in its last position, therebyselecting physiological transducer 174, display 48 indicates themeasured physiological information, such as blood pressure, heart beat,and the like, in digital format and in the color Cn. Measured values ofdifferent quantities are thus displayed in respectively differentcolors.

In FIG. 48 is shown an exemplary simplified schematic diagram of adigital multimeter capable of measuring signals from seven differentlocations and of indicating the measured results in seven differentcolors, respectively. The outputs Q0, Q1, Q2 of a 4-bit binary counter162 b, which may be from time to time incremented by a clock pulse, areconnected, in parallel, to the address inputs A, B, C of analogmultiplexers 147 a, 147 b, respectively, to cause the multiplexer 147 ato internally route signals from its selected input, e.g., Y1, to itsoutput Y, and, simultaneously, to apply 1the control voltage +VCC fromthe terminal Y of multiplexer 147 b, via its selected terminal, e.g.,Y1, to one of the color control inputs B to R. The measured signals fromthe selected location are indicated on display 40 in digital format andin a color unique to the selected location. The indicated colorsequences are merely exemplary; it would be obvious to devise othercolor sequences by differently interconnecting the terminals Y1 to Y7 ofmultiplexer 147 b with the color control inputs.

In FIG. 49 is shown a simplified schematic diagram of an AC digitalvoltmeter for selectively measuring an RMS (Root Mean Square) or MAV(Mean Average Value) of a measured waveform. An RMS measurement providesa power content of the measured signal, as will be more fully explainedlater, for a waveform of any shape. Since the MAV measured value maydiffer from the RMS value for certain waveform shapes, it would bedesirable to know which measurement method is employed. A switch 123 iselects either the output of RMS converter 181 or the output of theprecision rectifier circuit, consisting of an op amp 159 a, resistors124 x, 124 y, 124 z and diodes 128 a, 128 b, to the input of digitalvoltmeter 108. An associated switch 123 j selects one of the colorcontrol inputs C1, C2, in accordance with the selection of themeasurement method. The display 48 indicates the magnitude of themeasured AC waveform in digital format and in a color unique to theselected measurement method.

In FIG. 50 is shown a simplified schematic diagram of a digitalthermometer which can selectively measure temperature in the Kelvin,Celsius, or Fahrenheit scale, by connecting the output of one oftemperature transducers 177, 178, 179, via a switch 123 m, to the inputof digital voltmeter 108. An associated switch 123 n applies the controlvoltage +VCC to one of the color control inputs C1, C2, C3, of the colorcontrol circuit 52, to thereby illuminate display 48 in a color uniqueto the selected temperature scale. The output voltage of Kelvintemperature transducer 177 is linearly proportional to temperature inthe Kelvin scale. The output voltage of like Celsius temperaturetransducer 178 is linearly proportional to temperature in the Celsiusscale. The output voltage of like Fahrenheit temperature transducer 179is linearly proportional to temperature in the Fahrenheit scale.

In FIG. 51 is shown a simplified schematic diagram of a digitalampermeter with variable color range indication. The precision shuntresistors 126 a, 126 b, 126 c, 126 d, 126 e, connected in series,convert measured current to voltage, which is applied, via a resistor125 f of suitable value, to the input terminal of digital voltmeter 108.The current range is selectable by a rotary switch 123 a, in a mannerwell known to those skilled in the art. The invention resides in theaddition of a second rotary switch 123 b, associated with the switch 123a such that both switches are always in the same position, to connectthe reference voltage +VCC to the selected one of the color controlinputs, in accordance with the selected current range. The remainingcolor control inputs are tied to ground via suitable pull down resistors125 a, 125 b, 125 c, 125 d, 125 e. By way of an example, display 40 mayindicate measured current values on the 0.2 mA range in blue color, on 2mA range in purple color, on 20 mA range in green color, on 200 mA rangein yellow color, and on 2 A range in red color.

In FIG. 52 is shown a simplified schematic diagram of a digitalvoltmeter with variable color range indication. The precision voltageattenuating resistors 126 f, 126 g, 126 h, 126 i, 126 j are connected inseries, and the voltage range is selected by a rotary switch 123 c, in amanner well understood by those skilled in the art. The inventionresides in the addition of a second rotary switch 123 d, associated withthe switch 123 c, to apply the reference voltage +VCC to the selectedcolor control input. By way of an example, display 40 may indicatemeasured values on the 0.2 V range in white color, on 2 V range inyellow color, on 20 V range in green color, on 200 V range in blue-greencolor, and on 2000 V range in red color.

In FIG. 53 is shown a simplified schematic diagram of a digital ohmmeterwith variable color range indication. The precision standard resistors126 k, 126 m, 126 n, 126 p, 126 r, selectable by a rotary range switch123 e, are connected such that the selected one of the standardresistors is in series with the measured resistance Rx, in a well knownratiometric arrangement. The invention resides in the addition of asecond switch 123 f, associated with the switch 123 e, to connect thereference voltage +VCC to the selected one of the color control inputs,in accordance with the selected resistance range. By way of an example,display 40 may indicate measured resistance values on the 0.1 k range inyellow color, on 1 k range in green color, on 10 k range in blue color,on 100 k range in purple color, and on 1 M range in red color.

The examples of range and precision resistor values shown in FIGS. 51,52, 53 should be considered merely as exemplary. Although the switches123 are shown as rotary switches, they may, alternatively, be of anyother type, such are pushbutton switches and relay contacts. Anothermodification envisions that only certain of the display digits maychange color in accordance with the measurement range, while theremaining display digits may change color in accordance with a differentquantity. It is readily apparent that the principles of the inventionmay be effectively applied to autoranging multimeters.

In FIG. 54 is shown a detail of the multimeter of FIGS. 51, 52, 53 whichincludes a DVM chip 108 capable of converting analog voltage applied toits inputs HI and LO into signals for directly driving respectivesegments of a 3½ digit 7-segment variable color display 48. The colorcontrol 50 causes display 48 to illuminate in a selected color, asdescribed previously.

Commercially known digital multimeters are capable of indicatingnegative measured results, by displaying a small negative sign at themost significant digit, and positive measured results, usually by notdisplaying the minus sign. When a series of measurements is performed,it is difficult to distinguish between the positive and negativemeasurement results displayed on a long character string, particularlywhen the measurements are performed at a relatively fast rate. In FIG.55 is shown how this problem may be effectively solved by displayingpositive and negative measurement results in respectively differentcolors on a 3½ digit common cathodes variable color display 48, which iscapable of displaying a minus sign by illuminating the segment g in themost significant digit. The polarity output POL of digital voltmeter 108is directly connected to the color control input R, and, via an inverter151 a, to the color control input G, of the color control circuit 52.When the POL output is at a low logic level, to indicate that thedisplayed number is positive, the minus sign is extinguished. A lowlogic level at the POL output forces the output of the inverter 151 a torise to a high logic level, to activate the color control input G, tothereby illuminate display 48 in green color. When the POL output risesto a high logic level, to indicate that the displayed number isnegative, the minus sign is illuminated. A high logic level at the POLoutput activates the color control input R, to thereby illuminatedisplay 48 in red color. It would be obvious, in the view of the presentdisclosure, to devise other color combinations.

The description of a variable color digital display system shown in FIG.56, which is capable of emphasizing the position of a decimal point in astring of digits, should be considered together with its accompanyingtiming diagram shown in FIG. 57. The display system, which in itsexemplary embodiment utilizes eight single-digit variable color displays46 a to 46 h, which are only partially shown, is capable of detectingthe position of decimal point in a string of displayed digits and ofdisplaying all digits that precede the decimal point in a first colorand all digits that follow the decimal point in a second color. Thedecimal point outputs DP of common-cathodes 7-segment decoders 23 a to23 h, which may receive displayable data in a conventional manner (notshown), are continuously scanned in a sequence by a multiplexer 146which is incremented by a counter 162 d driven by clock 199 j of asuitable frequency. When an active high DP output is detected on certainof the decoders 23 a to 23 h, the inverting output W of multiplexer 146,which is connected to the set direct input SD of DP flip-flop 138 j,drops to a low logic level 199 n, to force the latter to its setcondition. The Q output of DP flip-flop 138 j, which is connected to theD inputs of all flip-flops 138 b to 138 h, rises to a high logic levelfor the remaining time of the scanning cycle, to thereby indicate, asmay be best observed in FIG. 57 in the line designated F—F 138 j QOUTPUT at waveform 199 p, the position of the detected decimal point inreference to the scanning cycle. A decoder 166 is incrementedsynchronously with the multiplexer 146, and, as a result, its outputs Y0to Y7 are sequentially driven to a low logic level, to trigger in asequence flip-flops 138 b to 138 h to states determined by theconditions of their D inputs, respectively, at the time of triggering,as may be best observed in FIG. 57 in the lines designated DEC 166OUTPUTS Y0 to Y7 at waveforms 190 a to 199 h. All flip-flops 138 b to138 h, which were triggered before the decimal point was located duringthe scanning cycle, are triggered to their reset states, while allremaining flip-flops 138 b to 138 h, which were triggered after thedecimal point was located, are triggered to their set states. The Y7output of the decoder 166 is connected to the clear direct input CD ofthe DP flip-flop 138 j, to force the latter to its reset condition atthe end of each scanning cycle. The outputs Q and {overscore (Q)} offlip-flops 138 b to 138 h are respectively connected to color controlinputs R and G of the color control circuits 52 b to 52 h, to therebycause all display digits 46 b to 46 h that precede the instant decimalpoint to be illuminated in green color, and all remaining display digitsthat follow the decimal point to be illuminated in red color. It wouldbe obvious that other color combinations may be devised.

The display system shown in FIG. 58 is capable of detecting the presenceor absence of decimal point in the displayed digital string, andaccordingly of displaying digital strings with decimal point (decimalnumbers) in a first color, and digital strings without decimal point(integers) in a different color. The decimal point outputs DP of allcommon-cathode 7-segment decoders 23 a to 23 h are respectivelyconnected to the inputs of an OR gate 154. When decimal point is presentin the displayed digital string, the appropriate DP output rises to ahigh logic level, thereby forcing the non-inverting output of OR gate154, which is connected to interconnected color control inputs R of allcolor control circuits 52 a to 52 h, to rise to a high logic level, tothereby cause all displays 46 a to 46 h to illuminate in red color. Whenno decimal point is detected in the displayed digital string, theinverting output of OR gate 154, which is connected to interconnectedcolor control inputs G of all color control circuits 52 a to 52 h, risesto a high logic level, to thereby cause all displays 46 a to 46 h toilluminate in green color.

In FIG. 59 is shown a block diagram of a variable color digital displaysystem for selectively indicating output values of seven digital devices12 a to 12 g in digital format and in respectively different colors. Theoutputs of digital devices 12 a to 12 g are respectively connected tothe inputs I1 to I7 of a digital multiplexer 146 b, which is addressedby a counter 161 c. Displayable digital data are routed from one of themultiplexer's inputs, selected by the instant output code of counter 161c, to its output Z and to variable color digital display element 43, tobe displayed thereon in digital format. The counter 161 c simultaneouslyaddresses color decoder 165 a, to activate one of seven color controlinputs B, P, BG, G, Y, W, R of color control circuit 53, in accordancewith the selected input of multiplexer 146 b. By way of an example, whenthe counter's output code 010 (binary) is applied to the address inputsof multiplexer 146 b, the input I2 is selected, and data from digitaldevice 12 b are indicated on display element 43 in digital format.Simultaneously, the counter's output code causes the output Y2 ofdecoder 165 a to be active, thereby activating the color control inputP, to cause display element 43 to illuminate in purple color. Digitaldevices 12 a to 12 g may include certain of those disclosed earlier.

In FIG. 60 is shown an expanded block diagram of a variable colordigital barometer with memory, for indicating measured values ofatmospheric pressure in digital format and in a color depending onprevious measured values. A scaling circuit consisting of op amps 159 c,159 d and resistors 124 a, 124 b, 124 c, 124 d, 124 e shifts and scalesoutput voltage of a pressure transducer 176, which is linearlyproportional to atmospheric pressure, such that voltage at the input ofdigital voltmeter 107 directly corresponds to the atmospheric pressure,either in milibars or in mm Hg, depending on the values of resistor 124e and V REF voltage. The digital voltmeter 107 converts the instantanalog voltage at its input to a digital code which is simultaneouslyapplied to variable color digital display 40, to be indicated thereon indigital format, and to the data input of a combined memory andcomparator 144, to be stored therein from time to time. The inventionresides in the addition of a color control circuit 50 for illuminatingdisplay 40 in a color depending on the result of comparison between theinstant measured value of atmospheric pressure and previously storedone, to thereby indicate whether the atmospheric pressure is eitherrising, or falling, or remains unchanged. A three-decade counter 164, orother suitable device for keeping time, is incremented in regularintervals by a clock, and its DIGITS outputs indicate the instant count.A decoder 165 b has its ADDRESS inputs connected, in a rather simplifiedmanner, to the counter's DIGITS outputs and utilizes the counter'sSELECT output as a strobe. As a result of continuous counting, atregular time intervals there will appear relatively short pulses 99 m atthe selected decoder's output Yn, which is connected to the LOAD inputof memory and comparator 144, to load the instant output data of digitalvoltmeter 107 into memory 144. The comparator 144 effects a comparisonof the data currently stored in its memory with the instant output dataof digital voltmeter 107 and accordingly develops output signals LT(Less Than), EQ (Equal), and GT (Greater Than). The comparator's outputsLT, EQ, GT are respectively connected to the color control inputs R, Y,G of color control circuit 50, to cause display 40 to illuminate in redcolor when the comparator's output LT is active (atmospheric pressure isfalling), in yellow color when the output EQ is active (atmosphericpressure is unchanged), and in green color when the output GT is active(atmospheric pressure is rising). The above description may serve as abackground for consideration of more sophisticated barometric systemscapable of comparing the instant measured values with values obtained byvirtue of arithmetic and logic operations, such are average or peakvalues of previous measurements, and of displaying measured values in avariety of colors depending on the rate of increase or decrease ofmeasured values.

In FIG. 61 is shown a block diagram of a digital multimeter 103 formaking series of measurements in combination with a clock 148 forkeeping time. The time signals developed by the clock circuit 148 aredecoded by a suitable time decoder 168 and converted to color controlsignals C1, C2 to Cn. The values measured by the multimeter 103 areindicated on display 40 in digital format and in a color having relationto time.

FlG. 62 is a block diagram of a multimeter which includes a memory 131,containing a reference measured value, and a comparator 141. Measuredvalues of input signal, which is applied to an input conditioningcircuit 120, wherein it may be switched, scaled, attenuated, rectified,and filtered (not shown), are compared with the reference value storedin memory 131 and indicated on display 40 in digital format and in acolor depending on the relationship between the measured value and thereference one. The memory 131 may include electronic storage elements,such are flip-flops, latches, RAMs, ROMs, and the like, and mechanicalstorage elements, such are binary switches or the like. When the instantmeasured value is less than the reference value, the output ‘<’ of thecomparator 141 is active, thereby activating the color control input C2of the color control circuit 50, to illuminate display 40 in the colorC2. When the instant measured value is greater than the reference one,the comparator's output ‘>’ is active, and the measured value isdisplayed in the color C1. Alternatively, the instant measured value maybe displayed in a color indicating its deviation, absolute or relative,from the reference value.

FIG. 63 is a block diagram of a multimeter which includes a memory 131 afor storing a low measurement limit, memory 131 b for storing a highmeasurement limit, and comparators 141 a, 141 b. The measured values arecompared with the high and low measurement limits and are indicated ondisplay 40 in digital format and in a color depending on therelationship between the measured value and the low and high measurementlimits. When the measured value is lower than the low measurement limit,stored in memory 131 a, the output ‘<’ of the comparator 141 a isactive, thereby activating the color control input C3 of the colorcontrol circuit 50, to illuminate display 40 in the color C3. When themeasurement value is higher that the high measurement limit, stored inmemory 131 b, the output ‘>’ of comparator 141 b is active, therebyactivating the color control input C1, to illuminate display 40 in thecolor C1. When the measured value is higher than the low measurementlimit and lower than the high measurement limit, the active outputs ‘>’of the comparator 141 a and ‘<’ of the comparator 141 b are combined ina logic fashion by a logic circuit 150, thereby activating the colorcontrol input C2, to illuminate display 40 in the color C2.

FIG. 64 is a block diagram of a multimeter for making repeatedmeasurements, which includes an A/D converter 106 and memory &comparator circuit 144. The instant measured value of the input signal,converted to digital format by the A/D converter 106, may be from timeto time stored in memory 144, so that subsequent measurements could becompared with the stored values. The instant measured value is displayedon display 40 in digital format and in a color depending on the resultof comparison with the value stored in the memory. When the instantmeasured value is less than that stored in the memory, the output LT(Less Than) of comparator 144 is active, thereby activating the colorcontrol input C3 of color control circuit 50, to display the measuredvalue in the color C3. When the instant measured value is equal to thatstored in the memory, the comparator output EQ (Equal) is active,thereby activating the color control input C2, to display the measuredvalue in the color C2. When the instant measured value is greater thanthat stored in the memory, the comparator output GT (Greater Than) isactive, thereby activating the color control input C1, to display themeasured value in the color C1.

FIG. 65 is a block diagram of a multimeter for making a series ofmeasurements and for comparing each measured value, by comparators 141a, 141 b, with low and high measurement limits stored in memories 131 a,131 b, respectively. An additional error memory 131 c, which may includean error counter, and logic circuit 150 a are provided for storing thenumber of measurement errors. The instant measured value is indicated ondisplay 40 in digital format and in a color depending, firstly, on itsrelationship with the applicable low and high measurement limits, and,secondly, on the number of previous measurement errors. Various kinds ofdecisions may be made, by a logic circuit 150 b, based on the contentsof the error memory. The decisions may be as simple as merely to displaythe measurement results in the color C1 for no previous measurementerrors and in the color C2 for some previous errors, or may involvesophisticated color selections based on the number of previous errorsand total number of measurements, arrived at by virtue of arithmetic andlogic operations.

In FIG. 66 is shown an exemplary simplified schematic diagram of thelimit memory and limit comparator combination, generally shown in FIG.65, for 8-bit measurement data (two BCD digits). The 8-bit data storedin a memory 132 a, symbolizing the low measurement limit, are applied torespective inputs B0 to B7 of a digital comparator 143 a; the 8-bit datastored in a like memory 132 b, symbolizing the high measurement limit,are applied to respective inputs B0 to B7 of a comparator 143 b. The8-bit measurement data, having relation to the instant measured value,are applied to respective inputs A0 to A7 of both comparators 143 a, 143b, interconnected in parallel. The comparators 143 a, 143 b effect acomparison between the measurement data and the instant low and highmeasurement limits and accordingly develop their output signals ‘<’,‘=’, ‘>’. When the instant measurement data are less than the lowmeasurement limit, the ‘<’ output of the comparator 143 a rises to ahigh logic level. When the instant measurement data are greater than thehigh measurement limit, the ‘>’ output of the comparator 143 b rises toa high logic level. When the instant measurement data are between thelow and high measurement limits, one of the inputs of each OR gate 152a, 152 b rises to a high logic level, thereby forcing both inputs of ANDgate 155 a to rise to a high logic level, which in turn forces theoutput of the latter to rise to a high logic level. The outputs PASS,FAIL LOW LIMIT, and FAIL HIGH LIMIT may be connected to respectiveinputs C1, C2, and C3 of the color control 50. By way of an example,display 40 may illuminate in green color for pass, in yellow color forfail on the low limit, and in red color for fail on the high limit.

In FIG. 67 is shown a simplified schematic diagram of the limit memory,limit comparator, and error memory combination, in a digital multimeterfor making a series of measurements. A memory 132 c contains datasymbolizing low measurement limits for each measurement step. A likememory 132 d contains data symbolizing high measurement limits for eachmeasurement step. An 8-bit counter 161, which is incremented for eachmeasurement step by a suitable clock pulse, is used to simultaneouslyaddress both memories 132 c, 132 d. When addressed for a particularmeasurement step, the memories 132 c, 132 d present the data residing atsuch address to the inputs B0, to B7 of comparators 143 c, 143 d,respectively, as the instant low and high measurement limits. Thecomparison of the instant measurement data with the instant measurementlimits is performed by comparators 143 c, 143 d at each measurementstep. When the measurement passes, the PASS output rises to a high logiclevel. When the measurement fails, either on the low or high measurementlimit, the FAIL output of OR gate 152 e rises to a high logic level, anderror memory 135 a is incremented by the next clock pulse. Thus theerror memory 135 a contains data representing the total number ofmeasurement errors. A logic circuit 150 b converts the instant errormemory data to color control signals C2 to Cn, whereby the instantmeasured value is displayed in the color C1 on pass, and in a certain ofthe colors C2 to Cn on fail, depending on the total number of previousmeasurement errors, as will be more fully explained later.

In FIG. 68 is shown a detail of the comparator, error flip-flop, andcolor control combination generally shown in FIG. 65. When a measurementerror occurs, either on the low or high measurement limit, the output ofan OR gate 152 f, which is connected to the D input of error flip-flop138 a, rises to a high logic level, and the error flip-flip will be setby the next clock pulse, to indicate that there was a measurement error.The error flip-flop may be suitably reset (not shown), e.g., at thebeginning of each measurement series. Results of the measurements areindicated on display 40 in digital format and in a color depending onthe result of comparison with the instant low and high measurementlimits and on the condition of the error flip-flop. By way of anexample, the measurements may be displayed in green color on pass, inyellow color on fail with no previous measurement errors, and in redcolor on fail with previous measurement errors.

FIG. 69 is another exemplary detail of the comparator, error memory, andcolor converter combination generally shown in FIG. 67. When ameasurement error occurs, the output of an OR gate 152 g, which isconnected to the DATA input of the error memory 135 b, rises to a highlogic level, and the error memory contents will be incremented by thenext clock pulse. The error memory 135 b thus contains data indicatingthe total number of previous measurement errors. The outputs of errormemory 135 b are applied to interconnected inputs of red color converter59 a, green color converter 59 b, and blue color converter 59 c, whichdevelop drive signals for energizing red bus 5, green bus 6, and bluebus 7 of display 40 to illuminate it in a color related to the totalnumber of previous errors.

FIG. 70 is a detail of the low limit memory and comparator combinationshown in FIG. 66. An 8-bit latch 134 stores data representing theinstant low measurement limit, which may be from time to time enteredvia its inputs D0 to D7 (not shown). Two 4-bit digital comparators 142a, 142 b are cascaded to form an 8-bit digital comparator, in a mannerwell understood by those skilled in the art.

FIG. 71 is an exemplary detail of the error counter and PROM combinationshown in FIG. 69. An 8-bit counter 163, which contains the countindicating the total number of previous measurement errors, is employedto address, via its outputs Q0 to Q7, a PROM 77 containing the colorconversion data which may be used to develop drive signals for red bus5, green bus 6, and blue bus 7, as previously shown in FIG. 35, tothereby illuminate display 40 in a color depending on the total numberof previous measurement errors.

The schematic diagram shown in FIG. 72 includes a digital multimeter 103for making repeated measurements of input signals and for developing atits outputs a 4-digit BCD code having relation to the magnitude of theinstant input signal, and two cascaded registered comparators 145 a, 145b for comparing the instant measured value with the value previouslystored. From time to time, a short positive pulse 99 n may be applied tointerconnected Load inputs S0, S1, to cause the instant data at theinputs I0 to I7 of both registered comparators 145 a, 145 b to be loadedtherein. The subsequent measured values will be compared with thereference value currently loaded in the register, and interconnectedoutputs LT (Less Than), EQ (Equal), GT (Greater Than), which are tied tothe supply voltage via suitable pull-up resistors 124 f, 124 g, 124 h,will indicate the result of each comparison. The comparator outputs arerespectively connected to the color control inputs C1, C2, C3 of thecolor control circuit 50, to control the color of display 40, shown inFIG. 62, in accordance with the result of the comparison. The display 40indicates the instant measured value in digital format and in a colordepending on the result of comparison with the reference value currentlystored in the register. By way of an example, display 40 may illuminatein green color when the instant measured value is equal to the referencevalue, in yellow color when it is less than the reference value, and inred color when it is larger than the reference value.

In FIG. 73 is shown a simplified schematic diagram of a digitalvoltmeter with 3½ digit variable color display. The digital voltmeter107 is configured, by having its initialize conversion input INITconnected to a high logic level, to continuously convert input analogvoltage, applied to its input terminal via a resistor 124 a, to 3½ digitBCD code corresponding to the magnitude of instant input voltage. TheBCD codes for the respective digits are converted, by 7-segment decoders22 a, 22 b, 22 c, 22 d, to signals for directly energizing the segmentsof the variable color display digits 42 a, 42 b, 42 c, 42 d,respectively, in a manner well understood by those skilled in the art.The color control circuit 50 causes all four display digits toilluminate uniformly in a selected color, as previously described.

A like block diagram shown in FIG. 74 differs in that four color controlcircuits 50 a, 50 b, 50 c, 50 d are employed to independently controlthe colors of respective display digits 42 a, 42 b, 42 c, 42 d.

In FIG. 75 is shown, in a block diagram configuration, a multimeterutilizing two digital voltmeters 109 a and 109 b for measuringrespective INPUT SIGNALS 1 and 2. The measured values of both inputsignals are simultaneously indicated on a single 8-digit variable colordisplay element 42 such that the four most significant display digits D1to D4 indicate the output of digital voltmeter 109 a, and the four leastsignificant display digits D5 to D8 indicate the output of digitalvoltmeter 109 b. In order to clearly distinguish between the twomeasured values, without the need for a visual gap therebetween, thecolor control circuit 52 a is adapted, by having its color control inputG connected to a high logic level, to illuminate the four mostsignificant display digits D1 to D4 in green color, and like colorcontrol circuit 52 b is adapted, by having its color control input Rconnected to a high logic level, to illuminate the four leastsignificant digits D5 to D8 in red color.

FIG. 76 is a block diagram of an RMS digital voltmeter with variablecolor crest factor indication. The RMS (Root Mean Square) value of themeasured waveform is its heating value when applied to a resistor; itindicates the magnitude of the measured waveform regardless of itsshape. The Crest Factor is the peak signal value divided by the RMSvalue; it indicates what type of a waveform it is.

The digital voltmeter includes an RMS converter 181 for converting aninput measured signal to a DC value representative of the energy contentof the measured signal. The DC value from the RMS converter 181 isapplied to the HI input terminal of a digital voltmeter 105 whichdevelops at its outputs signals to directly drive variable color digitaldisplay 40, to thereby indicate the measured RMS value in digitalformat, in a manner well known to those having ordinary skill in theart.

The invention resides in the addition of a crest factor converter 183for computing the crest factor value of the measured waveform, and of acolor converter 55 for controlling the color of display 40 in accordancewith the crest factor value. The RMS digital voltmeter of the presentinvention will simultaneously indicate the RMS value of the measuredwaveform in digital format and in a color indicative of the crest factorvalue of the measured waveform, to thereby simultaneously indicate itsmagnitude and shape.

FIG. 77 is a comparison chart of RMS and crest factor values for severalexemplary waveforms. It is readily apparent that the crest factor valueis a good indication of the waveform shape. The unity value of the crestfactor indicates that the measured signal is either a symmetricalwaveform or a DC signal. Small values of the crest factor (less than 2)usually indicate either a sine wave, triangle wave, or a low duty cyclepulse train. High values of the crest factor (greater than 4) usuallyindicate a noise signal or a pulse train with a high duty cycle.

As illustrated in FIG. 78, the crest factor converter 183 includes aratio producing circuit 187 that develops at its output RATIO A:B asignal representative of the ratio of signals applied to its inputs Aand B. The peak signal value, obtained from the output of the peakdetector 185, is applied to the input A. The RMS signal value, obtainedfrom the output of the RMS-to-DC converter 181, is applied to the inputB. The computed ratio of the peak signal value to the RMS signal value,developed at the output RATIO A:B, is by definition a crest factor valueof the measured signal.

In a simplified exemplary schematic diagram of a ratio producingcircuit, shown in FIG. 79, the output DC voltage of the RMS-to-DCconverter 181 is applied to the X1 input of a precision divider 188,while the output DC voltage of the peak detector 185 is applied to itsinput Z2. The precision divider 188 develops at its output suitablyscaled DC voltage representing the ratio of the signals Z2 to X1.

In an exemplary detail of the RMS converter circuit, shown in FIG. 80,the measured signal is applied, via suitable potentiometer 127 c, to theinput of an RMS-to-DC converter 182, which develops at its output a DCvoltage corresponding to RMS value of the measured signal. Thepotentiometer 127 b and resistors 124 p, 124 r are used to adjust offsetvoltage; the capacitor 129 p is selected to set a suitable averagingtime constant.

FIG. 81 is an exemplary detail of the peak detector circuit, in which ameasured signal is applied, via a suitable resistor 124 u, to the inputof a peak detector 186, which develops at its output a DC voltage,retained on the hold capacitor 129 r, representing the maximum value ofthe input signal. The present peak value may be from time to time reset,by applying a relatively short positive pulse 99 p to interconnectedinputs DET and RESET. When pulse 99 p returns to a low logic level, newpeak of the input signal may be measured.

As shown in FIG. 82 in a block diagram form, the output voltage of thecrest factor converter, which indicates the instant measured value ofthe crest factor, may be applied to input of a suitable comparator 141a, such as the one shown in FIG. 23, to develop color control logicsignals R, Y, G for the color control circuit 52, to illuminate displayelement 42 in one of three colors, in accordance with the value of thecrest factor. By way of an example, the comparator 141 a may be set todevelop active color control signal G for values of the crest factorless than 1.5, to illuminate display element 42 in green color, activecolor control signal Y for values of the crest factor between 1.5 and2.5, to illuminate display element 42 in yellow color, and active colorcontrol signal R for values of the crest factor greater than 2.5, toilluminate display element 42 in red color.

A similar block diagram shown in FIG. 83 differs in that a comparator141 b, such as the one shown in FIG. 25, and color control circuit 53are used to illuminate display element 43 in one of seven colors, inaccordance with the value of the crest factor. By way of an example, thecomparator 141 b may develop active color control signal B for values ofthe crest factor less than 1.1, to illuminate display element 43 in bluecolor, active color control signal P for values of the crest factorbetween 1.1 and 1.4, to illuminate display element 43 in purple color,active color control signal BG for crest factor values between 1.4 and1.7, to illuminate display element 43 in blue-green color, active colorcontrol signal G for crest factor values between 1.7 and 2.0, toilluminate display element 43 in green color, active color controlsignal Y for crest factor values between 2.0 and 2.5, to illuminatedisplay element 43 in yellow color, active color control signal W forcrest factor values between 2.5 and 3.0, to illuminate display element43 in white color, active color control signal R for crest factor valuesgreater than 3.0, to illuminate display element 43 in red color.

As shown in FIG. 84, the output voltage of the crest factor converter183 is applied to the input of a scaling circuit 80 a, such as the oneshown in FIG. 31, to be scaled and shifted to a voltage range suitablefor the continuous 2-primary color converter 57, which will developdrive signals for controlling red bus 5 and green bus 6, respectively,of display 42, to illuminate it in a color related -to the instantmeasured value of the crest factor.

A like block diagram shown in FIG. 85 differs in that 3-primary colorconverter 58 is used to develop drive signals for red bus 5, green bus6, and blue bus 7, respectively, of display element 43, to illuminate itin a color related to the measured value of the crest factor. Therelationship between the crest factor values and the color of displayelement 43 may be defined at will, e.g., by programming suitable datainto PROMs contained in color converter 58, as previously described.

In FIG. 86 is shown a front view of a digital multimeter which includesa 6½ digit variable color digital display 49, keyboard 117, and suitableterminals 116 for attaching thereto the measuring cords. The keyboard117 includes a DC V key 118 a for setting the multimeter to its DCvoltage mode, AC V key 118 b for setting the multimeter to its ACvoltage mode, OHMS key 118 c for setting the multimeter to its OHMSmode, RANGE keys 118 d, 118 e, 118 f, 118 g, 118 h, 118 i for settingthe multimeter to a selected range, LOCAL key 118 j for setting themultimeter to its local mode, FRONT key 118 k for selecting frontmeasurement terminals, FILTER key 118 m for setting the multimeter toits filter mode, AUTO key 118 n for setting the multimeter to itsautoranging mode, OFFS key 118 p, ‘%’ key 118 r, and LAH key 118 s forsetting the multimeter to certain of its mathematical modes. The HIINPUT terminal 116 a and LO INPUT terminal 116 b may be used for voltagemeasurements; the like HI OHM Terminal 116 c and LO OHM terminal 116 dmay be used for resistance measurements.

In FIG. 87 is shown a block diagram of a variable color digitalmultimeter controlled by a microprocessor or microcomputer 168, whichcan be influenced either locally, by entering commands via the keyboard117, or remotely, by sending commands over a bus via the remote controlcircuit 169. When properly commanded, the microprocessor 168 can controlthe input conditioning section 120, AC section 112, and OHMS section113, to selectively switch, scale, attenuate, rectify, and filter themeasured signals, before being applied to the input of an A/D converter106, which repeatedly performs analog-to-digital conversions anddevelops output data indicative of the magnitude of the instant measuredsignal. The microprocessor 168 can from time to time read output data ofthe converter 106 and send same to display controller 167, which causesthe data to be indicated on display 40 in digital format. The inventionresides in the addition of a color memory 136, wherein data symbolizinga selected color may be stored, and color control 50 for illuminatingdisplay 40 in the selected color. It is contemplated that the color ofdisplay 40 may be controlled in accordance with certain of the followingoperating modes:

a. Local/remote mode: The multimeter may be set either to its localmode, e.g., by actuating the LOCAL key 118 j on the front panel, whereinall commands are entered via the keyboard 117, and the remote control169 is disabled, or to its remote mode wherein all commands are sent viathe remote control 169, and the keyboard 117 is disabled. When in itslocal mode, microprocessor 168 will send data to the color memory 136commanding color control 50 to illuminate display 40 in a first color(e.g., green); when in its remote mode, microprocessor 168 will senddifferent data to color memory 136 commanding that display 40 beilluminated in a second color (e.g., red), so that an operator mayreadily distinguish the two modes.

b. Normal/offset mode: The multimeter may be set to its offset mode,e.g., by actuating the OFFS key 118 p on the front panel, wherein anumeric constant (an offset) is stored in the microprocessor's memory,to calculate and display the difference between a measured value and theoffset; when in its normal mode, the multimeter displays true measuredvalues. To indicate in which mode the multimeter currently operates, themicroprocessor 168 will send data to the color memory 136 commandingthat display 40 be illuminated in a first color when in its normal modeand in a second color when in its offset mode.

c. Standard/percent mode: The multimeter may be set to its percent mode,e.g., by actuating the ‘%’ key 118 r on the front panel, wherein apercent deviation of a measured value from a value stored in themicroprocessor's memory (reference value) is calculated and displayed;when in its standard mode, true measured values are displayed. Toindicate in which mode the multimeter currently operates, microprocessor168 will send data to color memory 136 commanding that display 40 beilluminated in a first color for the standard mode and in a second colorfor the percent mode.

d. LAH/standard mode: The multimeter may be set to its LAH (Low,Average, High) mode, e.g., by actuating the LAH key 118 s on the frontpanel, wherein the multimeter will store the most positive and mostnegative measured values, calculate the average measured value, andcount the number of measurements during the LAH cycle; when in itsstandard mode, true measured values are displayed. To indicate whetherthe multimeter currently operates in the standard or LAH mode, themicroprocessor 168 will send data to the color memory 136 commandingthat display 40 be illuminated in a first color for the standard modeand in a second color for the LAH mode.

In FIG. 88 is shown an expanded block diagram of a digital multimeterwith a DC section 111 for processing DC signals, AC section 112 forprocessing AC signals, and OHMS section 113 for performing resistancemeasurements, as will be more fully explained later. The multimeterincludes input terminals HI INPUT 116 a, LO INPUT 116 b, HI OHM 116 c,LO OHM 116 d on the front panel shown in FIG. 86, and like inputterminals on the rear panel (not shown), which may be selectivelyconnected to the input of a digital voltmeter 105. To select between thefront and rear measurements, the FRONT key 118 k may be actuated, whichtoggles a front/rear relay 191 between its energized and disenergizedconditions. To facilitate the illustration, a convention was adoptedthat a particular relay is designated in the drawings by a certainnumeral, and its associated contacts are designated by same numeral withcharacter ‘a’, ‘b’, etc., appended. By way of an example, relay 191 hascontacts 191 a, 191 b, 191 c, 191 d, 191 e. When relay 191 is notenergized, its contacts 191 a to 191 e are in the positions asillustrated, thereby making available the front input terminals forconnection to the input of digital voltmeter 105. When relay 191 isenergized, its contacts 191 a to 191 e switch to their other positions,respectively, thereby making available the rear input terminals forconnection to the input of the digital voltmeter 105. The inventionresides in the addition of relay contact 191 e, associated with contacts191 a to 191 d, such that the front and rear measurements are indicatedin a digital format and in respectively different colors. When themeasurements via the front input terminals are performed, asillustrated, relay contact 191 e is open, and the color control input C1is pulled to a low logic level by a suitable pull-down resistor 124 v,thereby forcing, via an inverter 151 e, the color control input C2 torise to a high logic level, to thereby cause display 40 to beilluminated in the color C2 (e.g., red). When the measurements via therear input terminals are performed, by causing relay 191 to be energizedto switch its contacts 191 a to 191 e to their other positions,respectively, contact 191 e is closed to apply a high logic level fromthe source +VCC to the color control input C1, and to simultaneouslyforce, via inverter 151 e, the color control input C2 to a low logiclevel, to thereby cause display 40 to be illuminated in the color C1(e.g., green).

In FIG. 89 is shown a like block diagram of a digital multimeter forselectively performing DC, AC, and OHMS measurements and for indicatingmeasured values in digital format and in respectively different colors.To perform DC measurements, the DC relay 192 is energized, e.g., byactuating the DC V key 118 a on the front panel of the, to connect theHI INPUT terminal, via contact 191 a and closed contact 192 a, and viathe DC section 111, to the HI input of digital voltmeter 105.Simultaneously, the LO relay 195 is energized to connect the LO INPUTterminal, via contact 191 b and closed contact 195 a, to the LO input ofdigital voltmeter 105. Measured DC values of the input signal areindicated on display 40 in digital format, in a manner well understoodby those skilled in the art. The invention resides in the provision of arelay contact 192 b, associated with contact 192 a, to apply a highlogic level to the color control input C1, to cause display 40 toilluminate in the color C1 (e.g., red).

To perform AC measurements, the AC relay 193 is energized, e.g., byactuating the AC V key 118 b on the multimeter's front panel, to connectthe HI INPUT terminal, via contact 191 a and closed contact 193 a, andvia the AC section 112, to the HI input of digital voltmeter 105.Simultaneously, LO relay 195 is energized to connect the LO INPUTterminal to the LO input of the digital voltmeter 105. Measured ACvalues of the input signal are indicated on display 40 in digitalformat, in a manner well understood. The relay contact 193 b, associatedwith contact 193 a, closes when relay 193 is energized, to apply a highlogic level to the color control input C2, to cause display 40 toilluminate in the color C2 (e.g., yellow).

To perform OHMS measurements, the OHMS relay 124 is energized, e.g., byactuating the OHMS key 118 c on the multimeter's front panel, to connectthe HI OHM terminal, via closed contact 194 a, and via OHMS section 113,to the HI input of digital voltmeter 105. The LO OHM terminal isconnected, via closed contact 194 b, to the LO input of digitalvoltmeter 105. Measured resistance values are indicated on display 40 indigital format, in a manner well known. The relay contact 194 c,associated with contacts 194 a, 194 b, closes when relay 194 isenergized, to apply a high logic level to the color control input C3, tocause display 40 to illuminate in the color C3 (e.g., green).

The digital voltmeter shown in FIG. 90 may be set to its filter modewherein the measured signal is filtered to remove high frequency noise.The invention resides in the addition of a filter flip-flop 138 b foractivating color control circuit 50 to illuminate display 40 in thecolor C1 for the filter mode turned on and in the color C2 for thefilter mode turned off. The filter mode may be turned on and off byactuating the FILTER key 118 m, to toggle filter flip-flop 138 b. Whenkey 118 m is actuated, its associated keyswitch 119 m momentarilycloses, to connect a low logic level to the trigger input TRG of a timer158, which is normally tied to a high logic level via its pull-upresistor 124 i, to produce at the timer's output OUT a relatively shortpositive going pulse 99 s, to trigger filter flip-flop 138 b to itsopposite state. The width of pulse 99 s may be set by selecting suitablevalues of resistor 124 z and capacitor 129 s, to eliminate the problemof possible bouncing of keyswitch 119 m. When flip-flop 138 b is in itsset condition, its output Q, which is connected to the input of a relaydriver 157, rises to a high logic level, to activate the latter, toenergize filter relay 196. The associated relay contact 196 a closes toconnect filter circuit 149 to the input of digital voltmeter 105. Theoutputs Q and {overscore (Q)} of flip-flop 138 b are connected to thecolor control inputs C1, C2, respectively, to cause display 40 toilluminate in a color in accordance with the condition of flip-flop 138b.

In brief summary, the invention describes a measuring system whichcomprises two devices for measuring two independent input signals andfor developing two sets of data indicative of the respective measuredvalues of the two signals. A single display device is provided whichincludes a plurality of side by side positioned variable color lightemitting diode digital display elements. The first set of the data isexhibited on certain of the display elements. The second set of the datais exhibited on the remaining of the display elements. A color controlis further provided for illuminating the first set of the data in afirst color, and the second set of data in a second color, in order todistinguish them comfortably.

It would be obvious, in the view of the present disclosure, that thehardware design of the present invention may be also implemented bysoftware. It would be further obvious that persons skilled in the artmay resort to modifications in the construction of the preferredembodiment described herein, without departing from the spirit and scopeof the invention as defined in the appended claims. It is contemplatedthat the principles of the invention are also applicable to numerousdiverse types of display devices, such as luminescent devices, liquidcrystal display devices, plasma display devices, cathode ray tubedisplay devices, and the like.

CORRELATION TABLE This is a correlation table of reference charactersused in the drawings herein, their descriptions, and examples ofcommercially available parts. # DESCRIPTION EXAMPLE  1 display segment 2 red LED  3 green LED  4 blue LED  5 red bus  6 green bus  7 blue bus10 device developing electric signals 11 analog voltage source 12digital device 15 segment body 16 light scattering material 20 decoder21 digital decoder driver 22 7-segment display decoder driver 23 commoncathode 7-segment decoder driver 4LS49 24 common anode 7-segment decoderdriver 74LS47 30 monochromatic digital display 40 variable color digitaldisplay 41 multiplexed variable color display 42 variable color7-segment display element (2 LEDs) 43 variable color 7-segment displayelement (3 LEDS) 46 variable color display element (2 LEDs) 47 variablecolor display element (3 LEDs) 48 3½ digit variable color display 49 6½digit variable color 7-segment display 50 color control 51 step variablecolor control 52 color control (2 LEDs) 53 color control (3 LEDs) 55color converter 56 continuously variable color converter 57 2-primarycolor converter 58 3-primary color converter 59 single color converter60 2-input OR gate 74HC32 61 4-input OR gate 4072 62 non-invertingbuffer 74LS244 63 inverting buffer 74LS240 64 inverter part of 74LS240,4 65 inverter 74HC04 66 2-input AND gate 74HC08 67 priority encoder74HC147 68 3-to-8 line decoder 74HC138 69 logic circuit 71 8-bit counter74F579 73 D type flip-flop 74HC74 74 A/D converter 75 8-bit A/Dconverter AD570 76 memory 77 2k × 8 bit PROM 2716 80 scaling circuit 81op amp LM741 82 analog comparator LM339 85 signal converter 90 resistor91 resistor 92 potentiometer 93 capacitor 99 pulse 101 multimeter 102multimeter with multiplexed outputs 103 digital multimeter 105 digitalvoltmeter 106 A/D converter 107 Teledyne DVM chip TSC8750 108 TeledyneDVM chip TSC71O7 109 Intersil DVM chip ILS7107 111 DC section 112 ACsection 113 OHMS section 115 control section 116 measuring terminal 117keyboard 118 key 119 keyswitch 120 input conditioning 121 selector 123rotary switch 124 resistor 125 resistor 126 precision resistor 127potentiometer 128 signal diode 1N4148 129 capacitor 131 memory 132 8-bitwide memory 134 8-bit latch 74HC273 135 error memory 136 color memory138 D-type flip-flop 74HC74 141 comparator 142 4-bit digital comparator74HC85 143 8-bit digital comparator 144 memory & comparator 145registered comparator 74F524 146 8-channel digital multiplexer 74HC151147 analog multiplexer 4051 148 clock 149 filter 150 logic circuit 151inverter 74HC04 152 2-input OR gate 74HC32 154 8-input OR/NOR gate74HC4078 155 2-input AND gate 74HC08 156 3-input AND gate 74HC11 157relay driver 1416 158 timer NE555 159 op amp LM741 161 counter 162 4-bitbinary counter 74HC161 163 8-bit binary counter 74F579 164 3-decadecounter 14553 165 decoder 166 1-to-8 lines decoder 74HC138 167 displaycontroller ICM7218A 168 microprocessor 8085 169 remote control 172temperature transducer 173 pressure transducer 174 physiologicaltransducer 176 SenSym pressure transducer LX18O2AN 177 Kelvintemperature transducer 178 Celsius temperature transducer LM35 179Fahrenheit temperature transducer LM34 181 RMS to DC converter 182 RMSconverter chip AD536A 183 crest factor converter 185 peak detector 186peak detector chip PKD-01 187 ratio producing circuit 188 precisiondivider chip AD535 191 front/rear relay JDT21 192 DC section relay JDT7193 AC section relay JDT7 194 OHMS section relay JDT15 195 LO inputrelay JWD-107 196 filter relay JWD-107 199 pulse

The examples of commercially available components should be consideredas merely illustrative. It will be appreciated that other components maybe readily and effectively used. The integrated circuits used in thedescription of the invention are manufactured by several well knowncompanies, such are Analog Devices, Inc., Fairchild Camera andInstrument Corporation, Intel Corporation, Intersil, Inc., MotorolaSemiconductor Products Inc., National Semiconductor Incorporated,Precision Monolithics Incorporated, Teledyne Semiconductor, TexasInstruments Inc., etc.

TABLE 1 DATA PORTIONS Input PROM ‘Red’ Voltage Address PROM (Volts)(Hex) (Hex) red green 0.0  00 00 0.0 1.0 0.039 01 00 0.0 1.0 0.078 02 000.0 1.0 0.117 03 00 0.0 1.0 0.156 04 00 0.0 1.0 0.195 05 00 0.0 1.00.234 06 00 0.0 1.0 0.273 07 00 0.0 1.0 0.312 08 00 0.0 1.0 0.352 09 000.0 1.0 0.391 0A 00 0.0 1.0 0.430 0B 00 0.0 1.0 0.469 0C 00 0.0 1.00.508 0D 00 0.0 1.0 0.547 0E 00 0.0 1.0 0.586 0F 00 0.0 1.0 0.625 10 400.25 0.75 0.664 11 40 0.25 0.75 0.703 12 40 0.25 0.75 0.742 13 40 0.250.75 0.781 14 40 0.25 0.75 0.820 15 40 0.25 0.75 0.859 16 40 0.25 0.750.898 17 40 0.25 0.75 0.937 18 40 0.25 0.75 0.977 19 40 0.25 0.75 1.0161A 40 0.25 0.75 1.055 1B 40 0.25 0.75 1.094 1C 40 0.25 0.75 1.133 1D 400.25 0.75 1.172 1E 40 0.25 0.75 1.211 1F 40 0.25 0.75 1.250 20 80 0.50.5 1.289 21 80 0.5 0.5 1.328 22 80 0.5 0.5 1.367 23 80 0.5 0.5 1.406 2480 0.5 0.5 1.445 25 80 0.5 0.5 1.484 26 80 0.5 0.5 1.523 27 80 0.5 0.51.562 28 80 0.5 0.5 1.602 29 80 0.5 0.5 1.641 2A 80 0.5 0.5 1.680 2B 800.5 0.5 1.719 2C 80 0.5 0.5 1.758 2D 80 0.5 0.5 1.797 2E 80 0.5 0.51.836 2F 80 0.5 0.5 1.875 30 C0 0.75 0.25 1.914 31 C0 0.75 0.25 1.953 32C0 0.75 0.25 1.992 33 C0 0.75 0.25 2.031 34 C0 0.75 0.25 2.070 35 C00.75 0.25 2.109 36 C0 0.75 0.25 2.148 37 C0 0.75 0.25 2.187 38 C0 0.750.25 2.227 39 C0 0.75 0.25 2.266 3A C0 0.75 0.25 2.305 3B C0 0.75 0.252.344 3C C0 0.75 0.25 2.389 3D C0 0.75 0.25 2.422 3E C0 0.75 0.25 2.4613F C0 0.75 0.25 2.500 40 FF 1.0 0.0 2.539 41 FF 1.0 0.0 2.578 42 FF 1.00.0 2.617 43 FF 1.0 0.0 2.656 44 FF 1.0 0.0 2.695 45 FF 1.0 0.0 2.734 46FF 1.0 0.0 2.773 47 FF 1.0 0.0 2.812 48 FF 1.0 0.0 2.852 49 FF 1.0 0.02.891 4A FF 1.0 0.0 2.930 4B FF 1.0 0.0 2.969 4C FF 1.0 0.0 3.008 4D FF1.0 0.0 3.047 4E FF 1.0 0.0 3.086 4F FF 1.0 0.0 3.125 50 00 0.0 1.03.164 51 00 0.0 1.0 3.203 52 00 0.0 1.0 3.242 53 00 0.0 1.0 3.281 54 000.0 1.0 3.320 55 00 0.0 1.0 3.359 56 00 0.0 1.0 3.398 57 00 0.0 1.03.437 58 00 0.0 1.0 3.477 59 00 0.0 1.0 3.516 5A 00 0.0 1.0 3.555 5B 000.0 1.0 3.594 5C 00 0.0 1.0 3.633 5D 00 0.0 1.0 3.672 5E 00 0.0 1.03.711 5F 00 0.0 1.0 3.750 60 40 0.25 0.75 3.789 61 40 0.25 0.75 3.828 6240 0.25 0.75 3.867 63 40 0.25 0.75 3.906 64 40 0.25 0.75 3.945 65 400.25 0.75 3.984 66 40 0.25 0.75 4.023 67 40 0.25 0.75 4.062 68 40 0.250.75 4.102 69 40 0.25 0.75 4.141 6A 40 0.25 0.75 4.178 6B 40 0.25 0.754.219 6C 40 0.25 0.75 4.258 6D 40 0.25 0.75 4.299 6E 40 0.25 0.75 4.3366F 40 0.25 0.75 4.375 70 80 0.5 0.5 4.414 71 80 0.5 0.5 4.453 72 80 0.50.5 4.492 73 80 0.5 0.5 4.531 74 80 0.5 0.5 4.570 75 80 0.5 0.5 4.609 7680 0.5 0.5 4.648 77 80 0.5 0.5 4.687 78 80 0.5 0.5 4.727 79 80 0.5 0.54.766 7A 80 0.5 0.5 4.805 7B 80 0.5 0.5 4.844 7C 80 0.5 0.5 4.883 7D 800.5 0.5 4.922 7E 80 0.5 0.5 4.961 7F 80 0.5 0.5 5.000 80 C0 0.75 0.255.039 81 C0 0.75 0.25 5.078 82 C0 0.75 0.25 5.117 83 C0 0.75 0.25 5.15684 C0 0.75 0.25 5.195 85 C0 0.75 0.25 5.234 86 C0 0.75 0.25 5.273 87 C00.75 0.25 5.312 88 C0 0.75 0.25 5.352 89 C0 0.75 0.25 5.391 8A C0 0.750.25 5.430 8B C0 0.75 0.25 5.469 8C C0 0.75 0.25 5.508 8D C0 0.75 0.255.547 8E C0 0.75 0.25 5.586 8F C0 0.75 0.25 5.625 90 FF 1.0 0.0 5.664 91FF 1.0 0.0 5.703 92 FF 1.0 0.0 5.742 93 FF 1.0 0.0 5.781 94 FF 1.0 0.05.820 95 FF 1.0 0.0 5.859 96 FF 1.0 0.0 5.898 97 FF 1.0 0.0 5.937 98 FF1.0 0.0 5.977 99 FF 1.0 0.0 6.016 9A FF 1.0 0.0 6.055 9B FF 1.0 0.06.094 9C FF 1.0 0.0 6.133 9D FF 1.0 0.0 6.172 9E FF 1.0 0.0 6.211 9F FF1.0 0.0 6.250 A0 00 0.0 1.0 6.289 A1 00 0.0 1.0 6.328 A2 00 0.0 1.06.367 A3 00 0.0 1.0 6.406 A4 00 0.0 1.0 6.445 A5 00 0.0 1.0 6.484 A6 000.0 1.0 6.524 A7 00 0.0 1.0 6.562 A8 00 0.0 1.0 6.602 A9 00 0.0 1.06.641 AA 00 0.0 1.0 6.680 AB 00 0.0 1.0 6.719 AC 00 0.0 1.0 6.758 AD 000.0 1.0 6.797 AE 00 0.0 1.0 6.836 AF 00 0.0 1.0 6.875 B0 40 0.25 0.756.914 B1 40 0.25 0.75 6.953 B2 40 0.25 0.75 6.992 B3 40 0.25 0.75 7.031B4 40 0.25 0.75 7.070 B5 40 0.25 0.75 7.109 B6 40 0.25 0.75 7.148 B7 400.25 0.75 7.187 B8 40 0.25 0.75 7.227 B9 40 0.25 0.75 7.266 BA 40 0.250.75 7.305 BB 40 0.25 0.75 7.344 BC 40 0.25 0.75 7.383 BD 40 0.25 0.757.422 BE 40 0.25 0.75 7.461 BF 40 0.25 0.75 7.500 C0 80 0.5 0.5 7.539 C180 0.5 0.5 7.587 C2 80 0.5 0.5 7.617 C3 80 0.5 0.5 7.656 C4 80 0.5 0.57.695 C5 80 0.5 0.5 7.734 C6 80 0.5 0.5 7.773 C7 80 0.5 0.5 7.812 C8 800.5 0.5 7.852 C9 80 0.5 0.5 7.891 CA 80 0.5 0.5 7.930 CB 80 0.5 0.57.969 CC 80 0.5 0.5 8.008 CD 80 0.5 0.5 8.047 CE 80 0.5 0.5 8.086 CF 800.5 0.5 8.125 D0 C0 0.75 0.25 8.164 D1 C0 0.75 0.25 8.203 D2 C0 0.750.25 8.242 D3 C0 0.75 0.25 8.281 D4 C0 0.75 0.25 8.320 D5 C0 0.75 0.258.359 D6 C0 0.75 0.25 8.398 D7 C0 0.75 0.25 8.437 D8 C0 0.75 0.25 8.477D9 C0 0.75 0.25 8.516 DA C0 0.75 0.25 8.555 DB C0 0.75 0.25 8.594 DC C00.75 0.25 8.633 DD C0 0.75 0.25 8.672 DE C0 0.75 0.25 8.711 DF C0 0.750.25 8.750 E0 FF 1.0 0.0 8.789 E1 FF 1.0 0.0 8.828 E2 FF 1.0 0.0 8.867E3 FF 1.0 0.0 8.906 E4 FF 1.0 0.0 8.945 E5 FF 1.0 0.0 8.984 E6 FF 1.00.0 9.023 E7 FF 1.0 0.0 9.062 E8 FF 1.0 0.0 9.102 E9 FF 1.0 0.0 9.141 EAFF 1.0 0.0 9.180 EB FF 1.0 0.0 9.219 EC FF 1.0 0.0 9.258 ED FF 1.0 0.09.299 EE FF 1.0 0.0 9.336 EF FF 1.0 0.0 9.375 F0 00 0.0 1.0 9.414 F1 000.0 1.0 9.453 F2 00 0.0 1.0 9.492 F3 00 0.0 1.0 9.531 F4 00 0.0 1.09.570 F5 00 0.0 1.0 9.609 F6 00 0.0 1.0 9.648 F7 00 0.0 1.0 9.687 F8 000.0 1.0 9.727 F9 00 0.0 1.0 9.766 FA 00 0.0 1.0 9.805 FB 00 0.0 1.09.844 FC 00 0.0 1.0 9.883 FD 00 0.0 1.0 9.922 FE 00 0.0 1.0 9.961 FF 000.0 1.0

TABLE 2 DATA PORTIONS Input PROM ′Red′ ′Green′ ′Blue′ Voltage AddressPROM PROM PROM (Volts) (Hex) (Hex) (Hex) (Hex) red green blue 0.0 00 FF00 00 1.0 0.0 0.0 0.039 01 FE 02 00 0.992 0.008 0.0 0.078 02 FC 04 000.984 0.016 0.0 0.117 03 FA 06 00 0.976 0.024 0.0 0.156 04 F8 08 000.969 0.031 0.0 0.195 05 F6 0A 00 0.961 0.039 0.0 0.234 06 F4 0C 000.953 0.047 0.0 0.273 07 F2 0E 00 0.945 0.055 0.0 0.312 08 F0 10 000.937 0.063 0.0 0.352 09 EE 12 00 0.930 0.070 0.0 0.391 0A EC 14 000.922 0.078 0.0 0.430 0B EA 16 00 0.914 0.086 0.0 0.469 0C E8 18 000.906 0.094 0.0 0.508 0D E6 1A 00 0.899 0.101 0.0 0.547 0E E4 1C 000.891 0.109 0.0 0.586 0F E2 1E 00 0.883 0.117 0.0 0.625 10 E0 20 000.875 0.125 0.0 0.664 11 DE 22 00 0.867 0.133 0.0 0.703 12 DC 24 000.859 0.141 0.0 0.742 13 DA 26 00 0.851 0.149 0.0 0.781 14 D8 28 000.844 0.156 0.0 0.820 15 D6 2A 00 0.836 0.164 0.0 0.859 16 D4 2C 000.828 0.172 0.0 0.898 17 D2 2E 00 0.820 0.180 0.0 0.937 18 D0 30 000.812 0.188 0.0 0.977 19 CE 32 00 0.804 0.196 0.0 1.016 1A CC 34 000.796 0.204 0.0 1.055 1B CA 36 00 0.788 0.212 0.0 1.094 1C C8 38 000.781 0.219 0.0 1.133 1D C6 3A 00 0.773 0.227 0.0 1.172 1E C4 3C 000.766 0.234 0.0 1.211 1F C2 3E 00 0.758 0.242 0.0 1.250 20 C0 40 00 0.750.25 0.0 1.289 21 BE 42 00 0.742 0.258 0.0 1.328 22 BC 44 00 0.734 0.2660.0 1.367 23 BA 46 00 0.726 0.274 0.0 1.406 24 B8 48 00 0.719 0.281 0.01.445 25 B6 4A 00 0.711 0.289 0.0 1.484 26 B4 4C 00 0.703 0.297 0.01.523 27 B2 4E 00 0.695 0.305 0.0 1.562 28 B0 50 00 0.687 0.313 0.01.602 29 AE 52 00 0.680 0.320 0.0 1.641 2A AC 54 00 0.672 0.328 0.01.680 2B AA 56 00 0.664 0.336 0.0 1.719 2C A8 58 00 0.656 0.344 0.01.758 2D A6 5A 00 0.648 0.352 0.0 1.797 2E A4 5C 00 0.641 0.359 0.01.836 2F A2 5E 00 0.633 0.367 0.0 1.875 30 A0 60 00 0.625 0.375 0.01.914 31 9E 62 00 0.613 0.383 0.0 1.953 32 9C 64 00 0.609 0.391 0.01.992 33 9A 66 00 0.602 0.398 0.0 2.031 34 98 68 00 0.594 0.406 0.02.070 35 96 6A 00 0.586 0.414 0.0 2.109 36 94 6C 00 0.578 0.422 0.02.148 37 92 6E 00 0.570 0.430 0.0 2.187 38 90 70 00 0.562 0.438 0.02.227 39 8E 72 00 0.554 0.446 0.0 2.266 3A 8C 74 00 0.547 0.453 0.02.305 3B 8A 76 00 0.539 0.461 0.0 2.344 3C 88 78 00 0.531 0.469 0.02.389 3D 86 7A 00 0.524 0.476 0.0 2.422 3E 84 7C 00 0.516 0.484 0.02.461 3F 82 7E 00 0.508 0.492 0.0 2.500 40 80 80 00 0.5 0.5 0.0 2.539 417C 84 00 0.484 0.516 0.0 2.578 42 78 88 00 0.469 0.531 0.0 2.617 43 748C 00 0.453 0.547 0.0 2.656 44 70 90 00 0.437 0.563 0.0 2.695 45 6C 9400 0.422 0.578 0.0 2.734 46 68 98 00 0.406 0.594 0.0 2.773 47 64 9C 000.391 0.609 0.0 2.812 48 60 A0 00 0.375 0.625 0.0 2.852 49 5C A4 000.359 0.641 0.0 2.891 4A 58 A8 00 0.344 0.656 0.0 2.930 4B 54 AC 000.328 0.672 0.0 2.969 4C 50 B0 00 0.312 0.688 0.0 3.008 4D 4C B4 000.297 0.703 0.0 3.047 4E 48 B8 00 0.281 0.719 0.0 3.086 4F 44 BC 000.266 0.734 0.0 3.125 50 40 C0 00 0.25 0.75 0.0 3.164 51 3C C4 00 0.2340.766 0.0 3.203 52 38 C8 00 0.219 0.781 0.0 3.242 53 34 CC 00 0.2030.797 0.0 3.281 54 30 D0 00 0.187 0.813 0.0 3.320 55 2C D4 00 0.1720.828 0.0 3.359 56 28 D8 00 0.156 0.844 0.0 3.398 57 24 DC 00 0.1410.859 0.0 3.437 58 20 E0 00 0.125 0.875 0.0 3.477 59 1C E4 00 0.1090.891 0.0 3.516 5A 18 E8 00 0.094 0.906 0.0 3.555 5B 14 EC 00 0.0780.922 0.0 3.594 5C 10 F0 00 0.062 0.938 0.0 3.633 5D 0C F4 00 0.0470.953 0.0 3.672 5E 08 F8 00 0.031 0.967 0.0 3.711 5F 04 FC 00 0.0160.984 0.0 3.750 60 00 FF 00 0.0 1.0 0.0 3.789 61 00 F8 08 0.0 0.9690.031 3.828 62 00 F0 10 0.0 0.937 0.063 3.867 63 00 E8 18 0.0 0.9060.094 3.906 64 00 E0 20 0.0 0.875 0.125 3.945 65 00 D8 28 0.0 0.8440.156 3.984 66 00 D0 30 0.0 0.812 0.188 4.023 67 00 C8 38 0.0 0.7810.219 4.062 68 00 C0 40 0.0 0.75 0.25 4.102 69 00 B8 48 0.0 0.719 0.2814.141 6A 00 B0 50 0.0 0.687 0.313 4.178 6B 00 A8 58 0.0 0.656 0.3444.219 6C 00 A0 60 0.0 0.625 0.375 4.258 6D 00 98 68 0.0 0.594 0.4064.299 6E 00 90 70 0.0 0.562 0.438 4.336 6F 00 88 78 0.0 0.531 0.4694.375 70 00 80 80 0.0 0.5 0.5 4.414 71 00 78 88 0.0 0.469 0.531 4.453 7200 70 90 0.0 0.437 0.563 4.492 73 00 68 98 0.0 0.406 0.594 4.531 74 0060 A0 0.0 0.375 0.625 4.570 75 00 58 A8 0.0 0.344 0.656 4.609 76 00 50B0 0.0 0.312 0.688 4.648 77 00 48 B8 0.0 0.281 0.719 4.687 78 00 40 C00.0 0.25 0.75 4.727 79 00 38 C8 0.0 0.219 0.781 4.766 7A 00 30 D0 0.00.187 0.813 4.805 7B 00 28 D8 0.0 0.156 0.844 4.844 7C 00 20 E0 0.00.125 0.875 4.883 7D 00 18 E8 0.0 0.094 0.906 4.922 7E 00 10 F0 0.00.062 0.938 4.961 7F 00 08 F8 0.0 0.031 0.967 5.000 80 00 00 FF 0.0 0.01.0 5.039 81 04 00 FC 0.016 0.0 0.984 5.078 82 08 00 F8 0.031 0.0 0.9695.117 83 0C 00 F4 0.047 0.0 0.953 5.156 84 10 00 F0 0.063 0.0 0.9375.195 85 14 00 EC 0.078 0.0 0.922 5.234 86 18 00 E8 0.094 0.0 0.9065.273 87 1C 00 E4 0.109 0.0 0.891 5.312 88 20 00 E0 0.125 0.0 0.8755.352 89 24 00 DC 0.141 0.0 0.859 5.391 8A 28 00 D8 0.156 0.0 0.8445.430 8B 2C 00 D4 0.172 0.0 0.828 5.469 8C 30 00 D0 0.188 0.0 0.8125.508 8D 34 00 CC 0.2 0.0 0.8 5.547 8E 38 00 C8 0.219 0.0 0.781 5.586 8F3C 00 C4 0.234 0.0 0.766 5.625 90 40 00 C0 0.25 0.0 0.75 5.664 91 44 00BC 0.266 0.0 0.734 5.703 92 48 00 B8 0.281 0.0 0.719 5.742 93 4C 00 B40.297 0.0 0.703 5.781 94 50 00 B0 0.313 0.0 0.687 5.820 95 54 00 AC0.328 0.0 0.672 5.859 96 58 00 A8 0.344 0.0 0.656 5.898 97 5C 00 A40.359 0.0 0.641 5.937 98 60 00 A0 0.375 0.0 0.625 5.977 99 64 00 9C0.391 0.0 0.609 6.016 9A 68 00 98 0.406 0.0 0.594 6.055 9B 6C 00 940.422 0.0 0.578 6.094 9C 70 00 90 0.438 0.0 0.562 6.133 9D 74 00 8C0.453 0.0 0.547 6.172 9E 78 00 88 0.469 0.0 0.531 6.211 9F 7C 00 840.484 0.0 0.516 6.250 A0 80 00 80 0.5 0.0 0.5 6.289 A1 84 00 7C 0.5160.0 0.484 6.328 A2 88 00 78 0.531 0.0 0.469 6.367 A3 8C 00 74 0.547 0.00.453 6.406 A4 90 00 70 0.563 0.0 0.437 6.445 A5 94 00 6C 0.578 0.00.422 6.484 A6 98 00 68 0.594 0.0 0.406 6.524 A7 9C 00 64 0.609 0.00.391 6.562 A8 A0 00 60 0.625 0.0 0.375 6.602 A9 A4 00 5C 0.641 0.00.359 6.641 AA A8 00 58 0.656 0.0 0.344 6.680 AB AC 00 54 0.672 0.00.328 6.719 AC B0 00 50 0.688 0.0 0.312 6.758 AD B4 00 4C 0.703 0.00.297 6.797 AE B8 00 48 0.719 0.0 0.281 6.836 AF BC 00 44 0.734 0.00.266 6.875 B0 C0 00 40 0.75 0.0 0.25 6.914 B1 C4 00 3C 0.766 0.0 0.2346.953 B2 C8 00 38 0.781 0.0 0.219 6.992 B3 CC 00 34 0.797 0.0 0.2037.031 B4 D0 00 30 0.813 0.0 0.187 7.070 B5 D4 00 2C 0.828 0.0 0.1727.109 B6 D8 00 28 0.844 0.0 0.156 7.148 B7 DC 00 24 0.859 0.0 0.1417.187 B8 E0 00 20 0.875 0.0 0.125 7.227 B9 E4 00 1C 0.891 0.0 0.1097.266 BA E8 00 18 0.906 0.0 0.094 7.305 BB EC 00 14 0.922 0.0 0.0787.344 BC F0 00 10 0.938 0.0 0.062 7.383 BD F4 00 0C 0.953 0.0 0.0477.422 BE F8 00 08 0.967 0.0 0.031 7.461 BF FC 00 04 0.984 0.0 0.016

What I claim is:
 1. A dual variable color measuring system comprising:first means for measuring a first signal and including a first dataoutput for developing first data indicative of a measured value of saidfirst signal; second means for measuring a second signal and including asecond data output for developing second data indicative of a measuredvalue of said second signal; a single display device including aplurality of light emitting diode display elements arranged in a side byside relation within said display device, each for providing a characterindication in a selective color, and each including a color controlinput for illuminating said character indication in a first color inresponse to a first color control signal and in a second color inresponse to a second color control signal; means, responsive to saidfirst data output, for providing a character indication of said firstdata on certain ones of said light emitting diode display elements;means, responsive to said second data output, for providing a characterindication of said second data on the remaining ones of said lightemitting diode display elements; first color control means, associatedwith said first means for measuring, for applying said first colorcontrol signal to those of said color control inputs, corresponding tosaid light emitting diode display elements on which said first data areexhibited, for illuminating said character indication of said first datain a first color; and second color control means, associated with saidsecond means for measuring, for applying said second color controlsignal to the remaining ones of said color control inputs, correspondingto said light emitting diode display elements on which said second dataare exhibited, for illuminating said character indication of said seconddata in a second color; whereby said character indication of said firstdata and said character indication of said second data are exhibited onsaid display device in a side by side relation and distinguished bydifferent colors.
 2. A dual variable color measuring system comprising:first means for measuring a first signal and including a first dataoutput for developing first data indicative of a measured value of saidfirst signal; second means for measuring a second signal and including asecond data output for developing second data indicative of a measuredvalue of said second signal; a single display device including a firstset of a plurality of light emitting diode display elements, associatedwith said first means for measuring, for providing a characterindication in a selective color, a first color control input coupled forilluminating said character indication on said first set in a firstcolor in response to a first color control signal, a second set of aplurality of light emitting diode display elements, associated with saidsecond means for measuring, for providing a character indication in aselective color, and a second color control input coupled forilluminating said character indication on said second set in a secondcolor in response to a second color control signal, said first set oflight emitting diode display elements and said second set of lightemitting diode display elements being arranged in a side by siderelation within said display device; means, responsive to said firstdata output, for providing a character indication of said first data onsaid first set of light emitting diode display elements; means,responsive to said second data output, for providing a characterindication of said second data on said second set of light emittingdiode display elements; first color control means, associated with saidfirst means for measuring, for applying said first color control signalto said first color control input, for illuminating said characterindication of said first data on said first set of light emitting diodedisplay elements in a first color; and second color control means,associated with said second means for measuring, for applying saidsecond color control signal to said second color control input, forilluminating said character indication of said second data on saidsecond set of light emitting diode display elements in a second color;whereby said character indication of said first data and said characterindication of said second data are exhibited on said display device in aside by side relation and distinguished by different colors.
 3. A dualvariable color measuring system comprising: first means for measuring afirst signal and including a first data output for developing first dataindicative of a measured value of said first signal; second means formeasuring a second signal and including a second data output fordeveloping second data indicative of a measured value of said secondsignal; a single display device including a plurality of light emittingdiode display elements, each for providing a character indication in aselective color, each including a color control input for illuminatingsaid character indication in a first color in response to a first colorcontrol signal and in a second color in response to a second colorcontrol signal, and all being arranged within said display device in aside by side relation to define the most significant light emittingdiode display elements and the least significant light emitting diodedisplay elements; means, responsive to said first data output, forproviding a character indication of said first data on said mostsignificant light emitting diode display elements; means, responsive tosaid second data output, for providing a character indication of saidsecond data on said least significant light emitting diode displayelements; first color control means, associated with said first meansfor measuring, for applying said first color control signal to the colorcontrol inputs of said most significant light emitting diode displayelements, for illuminating said character indication of said first datain a first color; and second color control means, associated with saidsecond means for measuring, for applying said second color controlsignal to the color control inputs of said least significant lightemitting diode display elements, for illuminating said characterindication of said second data in a second color; whereby said characterindication of said first data and said character indication of saidsecond data are exhibited on said display device in a side by siderelation and distinguished by different colors.
 4. A dual variable colormeasuring system comprising: first means for measuring a first signaland including a first data output for developing first data indicativeof a measured value of said first signal; second means for measuring asecond signal and including a second data output for developing seconddata indicative of a measured value of said second signal; a singledisplay device including a plurality of light emitting diode displayelements, each for providing a character indication in a selectivecolor, each including a color control input for illuminating saidcharacter indication in a first color in response to a color controlsignal of a predetermined logic level and in a second color in responseto a color control signal of an opposite logic level, and all beingarranged within said display device in a side by side relation to definethe most significant light emitting diode display elements and the leastsignificant light emitting diode display elements; means, responsive tosaid first data output, for providing a character indication of saidfirst data on said most significant light emitting diode displayelements; means, responsive to said second data output, for providing acharacter indication of said second data on said least significant lightemitting diode display elements; first color control means, associatedwith said first means for measuring, for applying a color control signalof said predetermined logic level to the color control inputs of saidmost significant light emitting diode display elements, for illuminatingsaid character indication of said first data in a first color; andsecond color control means, associated with said second means formeasuring, for applying a color control signal of said opposite logiclevel to the color control inputs of said least significant lightemitting diode display elements, for illuminating said characterindication of said second data in a second color; whereby said characterindication of said first data and said character indication of saidsecond data are exhibited on said display device in a side by siderelation and distinguished by different colors.
 5. A dual variable colormeasuring system comprising: first means for measuring a first signaland including a first data output for developing first data indicativeof a measured value of said first signal; second means for measuring asecond signal and including a second data output for developing seconddata indicative of a measured value of said second signal; a singledisplay device including a plurality of light emitting diode displayelements arranged in a side by side relation within said display device,each for providing a character indication in a selective color, and eachincluding a color control input for illuminating said characterindication in a first color in response to a first color control signaland in a second color in response to a second color control signal;means for decoding including a decoder input, for receiving input datadefining selected characters, and a plurality of decoder outputs, saiddecoder outputs being coupled to said light emitting diode displayelements in accordance with their positions in said display device, saiddecoder outputs producing selective decoder output signals forexhibiting the selected characters on said light emitting diode displayelements, in response to specific input data; means, responsive to saidfirst data output, for applying said first data to said decoder input,for providing a character indication of said first data on certain onesof said light emitting diode display elements; means, responsive to saidsecond data output, for applying said second data to said decoder input,for providing a character indication of said second data on theremaining ones of said light emitting diode display elements; firstcolor control means, associated with said first means for measuring, forapplying said first color control signal to those of said color controlinputs, corresponding to said light emitting diode display elements onwhich said first data are exhibited, for illuminating said characterindication of said first data in a first color; and second color controlmeans, associated with said second means for measuring, for applyingsaid second color control signal to the remaining ones of said colorcontrol inputs, corresponding to said light emitting diode displayelements on which said second data are exhibited, for illuminating saidcharacter indication of said second data in a second color; whereby saidcharacter indication of said first data and said character indication ofsaid second data are exhibited on said display device in a side by siderelation and distinguished by different colors.
 6. A dual variable colormeasuring system comprising: first means for measuring a first signaland including a first data output for developing first data indicativeof a measured value of said first signal; second means for measuring asecond signal and including a second data output for developing seconddata indicative of a measured value of said second signal; a singledisplay device including a first set of a plurality of light emittingdiode display elements arranged in a side by side relation within saiddisplay device and associated with said first means for measuring, forproviding a character indication in a selective color, a first colorcontrol input coupled for illuminating said character indication on saidfirst set in a first color in response to a first color control signal,a second set of a plurality of light emitting diode display elementsarranged in a side by side relation within said display device andassociated with said second means for measuring, for providing acharacter indication in a selective color, and a second color controlinput coupled for illuminating said character indication in a secondcolor in response to a second color control signal; means for decodingincluding a decoder input, for receiving input data defining selectedcharacters, and a plurality of decoder outputs, said decoder outputsbeing coupled to said light emitting diode display elements inaccordance with their positions in said display device, said decoderoutputs producing selective decoder output signals for exhibiting theselected characters on said light emitting diode display elements, inresponse to specific input data; means, responsive to said first dataoutput, for applying said first data to said decoder input, forproviding a character indication of said first data on said first set oflight emitting diode display elements; means, responsive to said seconddata output, for applying said second data to said decoder input, forproviding a character indication of said second data on said second setof light emitting diode display elements; first color control means,associated with said first means for measuring, for applying said firstcolor control signal to said first color control input, for illuminatingsaid character indication of said first data on said first set of lightemitting diode display elements in a first color; and second colorcontrol means, associated with said second means for measuring, forapplying said second color control signal to said second color controlinput, for illuminating said character indication of said second data onsaid second set of light emitting diode display elements in a secondcolor; whereby said character indication of said first data and saidcharacter indication of said second data are exhibited on said displaydevice in a side by side relation and distinguished by different colors.7. A dual variable color measuring system comprising: first means formeasuring a first signal and including a first data output fordeveloping first data indicative of a measured value of said firstsignal; second means for measuring a second signal and including asecond data output for developing second data indicative of a measuredvalue of said second signal; a single display device including aplurality of light emitting diode display elements, each for providing acharacter indication in a selective color, each including a colorcontrol input for illuminating said character indication in a firstcolor in response to a first color control signal and in a second colorin response to a second color control signal, and all being arrangedwithin said display device in a side by side relation to define the mostsignificant light emitting diode display elements and the leastsignificant light emitting diode display elements; means for decodingincluding a decoder input, for receiving input data defining selectedcharacters, and a plurality of decoder outputs, said decoder outputsbeing coupled to said light emitting diode display elements inaccordance with their positions in said display device, said decoderoutputs producing selective decoder output signals for exhibiting theselected characters on said light emitting diode display elements, inresponse to specific input data; means, responsive to said first dataoutput, for applying said first data to said decoder input, forproviding a character indication of said first data on said mostsignificant light emitting diode display elements; means, responsive tosaid second data output, for applying said second data to said decoderinput, for providing a character indication of said second data on saidleast significant light emitting diode display elements; first colorcontrol means, associated with said first means for measuring, forapplying said first color control signal to the color control inputs ofsaid most significant light emitting diode display elements, forilluminating said character indication of said first data in a firstcolor; and second color control means, associated with said second meansfor measuring, for applying said second color control signal to thecolor control inputs of said least significant light emitting diodedisplay elements, for illuminating said character indication of saidsecond data in a second color; whereby said character indication of saidfirst data and said character indication of said second data areexhibited on said display device in a side by side relation anddistinguished by different colors.
 8. A dual variable color measuringsystem comprising: first means for measuring a first signal andincluding a first data output for developing first data indicative of ameasured value of said first signal; second means for measuring a secondsignal and including a second data output for developing second dataindicative of a measured value of said second signal; a single displaydevice including a plurality of light emitting diode display elements,each for providing a character indication in a selective color, eachincluding a color control input for illuminating said characterindication in a first color in response to a color control signal of apredetermined logic level and in a second color in response to a colorcontrol signal of an opposite logic level, and all being arranged withinsaid display device in a side by side relation to define the mostsignificant light emitting diode display elements and the leastsignificant light emitting diode display elements; means for decodingincluding a decoder input, for receiving input data defining selectedcharacters, and a plurality of decoder outputs, said decoder outputsbeing coupled to said light emitting diode display elements inaccordance with their positions in said display device, said decoderoutputs producing selective decoder output signals for exhibiting theselected characters on said light emitting diode display elements, inresponse to specific input data; means, responsive to said first dataoutput, for applying said first data to said decoder input, forproviding a character indication of said first data on said mostsignificant light emitting diode display elements; means, responsive tosaid second data output, for applying said second data to said decoderinput, for providing a character indication of said second data on saidleast significant light emitting diode display elements; first colorcontrol means, associated with said first means for measuring, forapplying a color control signal of said predetermined logic level to thecolor control inputs of said most significant light emitting diodedisplay elements, for illuminating said character indication of saidfirst data in a first color; and second color control means, associatedwith said second means for measuring, for applying a color controlsignal of said opposite logic level to the color control inputs of saidleast significant light emitting diode display elements, forilluminating said character indication of said second data in a secondcolor; whereby said character indication of said first data and saidcharacter indication of said second data are exhibited on said displaydevice in a side by side relation and distinguished by different colors.